S. Ceres, vultur, Circe, passer, Herculea, harpya, Hecate, tumida, concentrica, Helmerseni, Puschana, decussata, plebeia, Ferronesensis, Ezquerra, Hispanica, Toreno, subconcentrica, Pelapayensis, Campomanensis, Mayendorfi, Roissyi, serpentina, lamellosa, ambigua, Blodena, planosulcata, expansa, pentaëdra, pectinifera, trigonella, quinquecostata, quadricostata, tricostata and cristigalli.

Several of the above species do not belong to the group. This list shows that D'Orbigny regarded the genus as including not only the types of Athyris and Spirigera but also that of the genus Merista (M. Herculea) which I shall notice farther on. I think it quite certain that had D'Orbigny been aware that the genus was capable of subdivision, he would have retained Athyris for one of the groups which have the beak imperforate. Indeed, according to the laws of nomenclature, he could not have done otherwise with any probability of producing a permanent classification.

In a valuable paper, read before the Geological Society of France, in May, 1848, on the Brachiopoda of the Upper Silurian rocks of England,* Mr. Davidson made the following observations on D'Orbigny's genus:

Vient ensuite le genre Spirigera que le même auteur établit pour les coquilles qui possédent des spires internes placés de la même manière que les Spirifer, mais qui ont des appendices et des détails d'organisation essentiellement différents. Ces espèces, parmi lesquelles nous trouvons les Terebratula, tumida, Circe, concentrica, subconcentrica, Roissyi, pectinifera, ambigua, Helmerseni, Pelapayensis, Campomanensis, Ferronesensis, Ezquerra, Hispanica, ont déjà été distinguées par M. de Verneuil comme devant former une section à part, qu'il a nommée la section des Concentrica. Je suis de l'opinion de M. d'Orbigny qu'elles doivent constituer un genre. L'étude minutieuse que M. Bouchard a faite de la Terebratula concentrica ne m'en laisse aucun doute; mais ce genre n'ayant pas encore été convenablement caractérisé, je m'abstiendrai de l'adopter dans ce petit mémoire qui n'est pour ainsi dire qu'un résumé d'un plus grand travail que je publie en ce moment dans le London Geological Journal.

Upon the above I shall only remark that it is quite clear that Mr. Davidson then regarded S. concentrica and A. tumida as congeneric; and that whatever new genus might be established, it would include both species.

In 1852, McCoy, in the 2nd Fasciculus of the "British Paleozoic Fossils," page 196, re-defined Athyris as follows:

"Gen. Ch.-Nearly orbicular or ovate, both valves convex; no cardinal area, foramen, or hinge-line: spiral appendages to beak of entering valve very large, nearly filling the shell; a strong mesial septum in the rostral part of entering valve; dental lamella moderate; tissue of shell apparently fibrous.

Mémoire sur les Brachiopodes du Système Silurien supérieur d'Angleterre, par M. Th. Davidson, Bull. Geol. Soc. Fr., v, pp. 309, 314.

"One specimen (of A. tumida) shows the pallial and ovarian impressions to be thick, numerous, and dichotomising frequently from beak to margin."

In the work cited and in the 3d Fasciculus, we find the following species:-A. tumida, S. concentrica, ambigua, De Roissyi, expansa, globistriata, globularis, gregaria, paradoxa, pectinifera, and squamigera. This shows clearly enough his views of the extent of the genus, that is to say, that as it was then understood, it included both A. tumida and A. concentrica. In commenting on this, Prof. Hall says:-"The fact that McCoy cited this as an Athyris, no more renders it an Athyris than it was made Atrypa, by being thus described by Dalman; and it was just as free for the foundation of a genus after the citation of McCoy as before." This is true enough, in part. It was free for the foundation of a genus until 1853, when Davidson used it for that purpose; but since 1853, it has never been free.

The above is quite sufficient to prove my first and second propositions.

I am not aware that any thing else of much importance, with the exception of what relates to Merista, having been published up to 1853, when Davidson's excellent work, the "Introduction to the Classification of the Brachiopoda," made its appearance, in which the genus was first subdivided. But, before entering upon this, I shall notice the remarks of Prof. Suess, on the genus Merista.

This genus was proposed by Prof. Suess, in 1851, but he did. not then sufficiently characterize it. The following is all that I can find, relating to it, that was published previously to 1853.

"Mr. E. Suess communicated the results of the investigations on several Brachiopods, from the Bohemian transition rocks, which had been made by him and Mr. Custos Dormitzer, of Prague. He showed that some of the forms heretofore referred to Terebratula had no opening in the beak, for the passage of the muscle of adhesion; and, also, that the distribution of their inner organs points to an affinity with the non-attached genus Pentamerus. These inner organs are borne by six partitions in place of a single calcareous loop; the spiral arms are not unrollable.

"Through the separation of these forms (for which the name Merista is proposed) from the genus Terebratula, an apparent contradiction in the laws of paleontological distribution is solved, since these smooth forms will now be separated, which have heretofore offered an apparent contradiction to the present views of these laws."

Lest I should not have expressed his views rightly in this free translation, I give the original in the note below.t

This Jour. II, xxxii, 131.

"Herr Eduard Suess theilte die Erfolge der Untersuchung einiger Brachiopoden aus dem böhmischen Uebergangsgebirge mit, die er gemeinschaftlich mit Herrn Custos Dormitzer in Prag angestellt hatte. Er zeigte, dass mehrere bisher zu den

On page 160 of the same work, there are some farther remarks on the classification of the brachiopoda, by Prof. Suess, in which he refers to the genus Merista. No generic description is, however, there given. It appears also that it was again noticed in "Leonhard's Neues Jahrbuch, p. 127, 1854." I have not, at present, access to that work, and do not know whether the genus is described there or not: at all events, at the time Mr. Davidson prepared the English edition of his "General Introduction," Merista was not understood.

Prof. King in his "Monograph of the Permian fossils of England" (1850) proposed to restore the genus Cleiothyris of Phillips, apparently making it partly equal to Athyris McCoy. But the specimen on which this arrangement was founded, was afterward shown to Mr. Davidson, and by him identified with T scalprum Barrande (now Merista scalprum), while Cleiothyris was intended by its author as a substitute for Atrypa. (See Davidson's Introduction, p. 85.)

2. Subdivision of the Genus by Mr. Davidson in 1854.-From all the facts above given it may be gleaned that in 1853, when Mr. Davidson was engaged in the preparation of his General Introduction, this group of Brachiopoda was known as a single genus but with two generic names Athyris McCoy, 1844; Spirigera D'Orbigny, 1847. Each of these was intended by its author to include the whole group. McCoy was under the impression that all the species had the beak imperforate, while D'Orbigny maintained that they were all perforated. authors were partly wrong and partly right. The genus was capable of subdivision, but no one had as yet undertaken that task; unless indeed, the observations of Prof. King and Suess can be so construed. With regard to the latter, as the genus Merista is now well understood and is different from Athyris, it does not affect the question. Cleiothyris may be considered as obsolete.

Both

Mr. Davidson in his "General Introduction" in endeavoring to reconcile the conflicting nomenclatures of D'Orbigny and McCoy divided the genus, retaining the name Athyris for "forms with an apparently imperforate beak or closed foramen, variously disposed septa and largely developed dental plates.

He

Terebrateln gezählte Formen an ihrer Spitze keine Oeffnung für den Anheftungsmuskel besitzen, und dass auch die Vertheilung ihrer inneren Organe auf eine Verwandtschaft mit der ebenfalls nicht angehefteten Gattung Pentamerus hinweist. Diese inneren Organe werden von 6 Wänden, statt von einer einfachen Kalkschleife getragen; die Spiralarme selbst sind nicht aufrollbar."

Durch das Lostrennen dieser Formen, für welche der Name Merista vorgeschlagen wird, von der Gattung, Terebratula, wird zugleich ein scheinbarer Widerspruch in den Gesetzen paläontologischer Verbreitung gehoben, da eben jene glatten Arten ausgeschieden werden, welche den bisherigen Ansichten über diese Gesetze am schroffstan entgegengestanden waren."-Jahrbuch der k. k. geologischen Reichsanstalt, Vienna, ii, pt. 4, pp. 150, 160. 1851.

selected two species, "A. tumida Dal. or Herculea Barrande," and specially named them as the types.

He retained Spirigera for the group of which S. concentrica is the type. As to this latter group, by whatever name it may be hereafter known, its extent will most probably always be that assigned to it in the work in question.

The genus Athyris, however, as there defined, included Merista, a circumstance which, however, as I shall presently show, in no way vitiates the arrangement. In a note, he states,-"before coming to the above conclusion, I submitted my views to Mr. Deshayes, Mr. Salter, and others, who seemed to consider that this mode of compromising the difficulty could not reasonably be objected to by the two authors principally concerned nor by the generality of Paleontologists." Op. cit., p. 86.

Afterward this classification was strongly objected to by several naturalists, who maintained that McCoy had "originally and positively" applied the name Athyris to the S. concentrica group, and, therefore, it could not be transferred to the other principal section. He, therefore, in the French edition of this introduction (1856), abandoned his first arrangement,* and substituted Merista and Athyris, at the same time transferring the latter to Spirigera, as in the extract given in the note below. (Op. cit., p. 101.)

Upon a careful examination of all the circumstances I think it will be found that according to the laws of nomenclature this change cannot be sustained. I shall therefore quote some of those laws and endeavor to apply them to this case.

The first rule reads thus:

"S. 1.-The name originally given by the founder of a group or the describer of a species, should be permanently retained, to the exclusion of all subsequent synonyms."

It seems scarcely necessary to quote such a rule as this. I only do so in order to make the comment, that it is the most important of all the laws of nomenclature; and that its operation cannot be prevented in any case, by merely technical objections or by any error in the details of a generic or specific description. Provided the original diagnosis contains sufficient in substance, to enable the scientific public to identify the group, trivial errors, from which the writings of no naturalist are free,

* "Mais ce moyen terme a été critiqué par plusieurs naturalistes qui ont insisté sur ce que le terme Athyris avait été originairement et positivement appliqué par son auteur a la T. concentrica et sur l'impropriété de l'autre dénomination pour désigner des coquelles telles que les T. tumida, Herculea, &c. M. Suess nous a informé (2) qu'il avait, en 1851, proposé le nom de Merista (3) pour le groupe ren ferment ces derniers. J'abandonne donc la proposition que j'avais faite en 1853, et je conserve indifféremment l'Athyris McCoy, ou le Spirigera d'Orb., pour le T. concentrica; et Merista, Suess, pour les T. tumida, Herculea, etc. (2) Neues Jahrbuch, p. 62, janvier, 1854. (3) Jahrb. k. k. geol. Reichsanstalt, II, IV, 150, 1851. Mentionné encore dans Leonhard's neues Jahrbuch, p. 127, 1854."

will not have any effect. All that can be done is to rectify; not to destroy. One of the exceptions to this rule is thus expressed in No. 11. "A name may be changed when it implies a false proposition which is likely to propagate important errors.' According to this exception if the name Athyris should be applied to the S. concentrica group there is a possibility of its falling into the list of synonyms; for, although no very important error would be superinduced, yet few naturalists can apply it to shells with a well defined foramen without feeling that such an application is to some extent, inconsistent with the purity of scientific nomenclature.

"§ 3. A generic name, when once established, should never be cancelled in any subsequent subdivision of the group, but retained in a restricted sense for one of the constituent portions.'

"4-A generic name should always be retained for that portion of the original genus which was considered typical by the author."

This latter rule is preceded by some introductory observations which should be embodied in it as they in fact form a part of the rule itself. They are especially applicable to this

case.

"When a genus is subdivided into other genera, the original name should be retained for that portion of it as at first defined. Authors frequently indicate this by selecting some one species as a fixed point of reference, which they term the "type of the genus." When they omit doing so, it may still in many cases be justly inferred that the first species mentioned on the list, if found accurately to agree with their definition, was regarded by them as the type. A specific name, or its synonyms, will also often serve to point out the particular species which by implication must be regarded as the original type of the genus. In such cases we are justified in restoring the name of the old genus to its typical signification, even when later authors have done otherwise."

Now this rule bears directly on the question, because many naturalists are under the impression that the first species placed on the list must necessarily be regarded as the type, where the author is silent on that point. But according to the above (and common sense), it is only so if found accurately to agree with the definition. Spirigera concentrica does not agree either with the name Athyris, nor with McCoy's generic description, nor with his typical figure. Therefore it cannot be arbitrarily selected as the type, and the name Athyris, in consequence, retained for that group. Indeed in many instances it would be impossible that the first species placed in the genus should be the type, for the author might not have the true type in the collection under investigation.

In this instance, as before mentioned, McCoy was preparing a work exclusively devoted to Carboniferous fossils, among

AM. JOUR. SCI.-SECOND SERIES, VOL. XLIV, No. 130.-JULY, 1867.