260 TWENTIETH REPORT ON THE STATE CABINET. 



*' made larger than it is in the original figure ;"* at the same time forgetting 

 to tell us that it is given by Davidson as Athyris concentrica and not 

 Spirigera concentrica. All this is very u7isophisticated. 



It is scarcely necessary to inform the student of palaeontology that 

 Prof. M'CoY placed Terehratula tumida of Dalman under his Genus 

 Athyris only in 1852, in his work on the British Palasozoic Fossils, as 



follows : 



''GenxLs ATHYRIS (M'Coy), 1844." 

 '' Syn.=S/;mgem (D'Orb.), 1848." 



— Thus recording his own view of the matter in citing Spirigera, without 

 comment or qualification, as a synonym of Athyris; a fact which Mr. 

 Billings has forgotten or omitted to state.! 



Mr. Billings, how(^ver, undertakes to tell us the operations of Prof. 

 M'Coy's mind, and what he knew or thought upon the subject; some por- 

 tions of which are interesting, though we acknowledge our inability to 

 entirely comprehend the first sentence of the following paragraph. After 

 quoting M'Coy's description of the genus Athyris, and his remarks upon 

 this group of shells from page 146 of Carboniferous Fossils of Ireland (1844), 

 he proceeds as follows : 



" The above is all that he wrote about the genus at that time ; and it will be per- 

 ceived that he does not point out any particular species as the type, and, further, 

 that there is nothing m his remarks from which it can be inferred that he knew 

 anything about the genera into which the group was afterwards subdivided.^ Conse- 

 quently it is impossible that he could have intended to confine the genus to any one 

 of them, as is now aflflrmed hy some of the naturalists Avho are opposed to the 

 classification ^advocated in this paper. Instead of excluding species with an imper- 

 forate beak such as A. tumida, the etymology of the word Athyris (without a door 

 or opening), the expression ' in which there is no vestige of either foramen, cardi- 

 nal ^.rea or hinge-line/ and, also, his typical figures all induce the belief that he had 

 before him one or more forms with the beak entire. This is rendered certain by 

 what he says on page 147. Speaking of what he calls A. concentrica, he says : ' This 

 species is not uncommon; it is figured in the Bull, de la Soc. Geol. de France, with 

 a perforated beak as in Terehratula. I have, however, seen numerous specimens with 

 the beak entire and imperforate, as in the other paleozoic species.' It is highly 

 probable, from all this, that he had in view such Silurian forms as A. tumida. This 

 latter species is so common that it is almost certain that such a collection, as he was 

 then engaged upon, would contain one or more specimens." 



* "Fig. 2. — Spirigera concentrica, Von Buck. The form is copied from Davidson's 

 Monograph of the British Devonian Brachiopoda, Vol. iii, fig. 13, Pal. Soc. for 1862. 

 The right hand side is, in this copy, a little restored, and the aperture in the beak made 

 larger than it is in the original figure." 



f Following the citation above, Prof. M'Coy gives an amended description of the 

 Genus Athyris, which differs somewhat from that published in 1844, and is as follows : 



''Gen. char. — 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 rostral jjart of entering valve ; 

 *' dental lamellae moderate; tissue of shell apparently fibrous." 



[ f Is it necessary that an author should kncfw what is afterwards to be discovered, in 

 order to understand what he intends to do at the present time ?] 



* See note ou page 378 of British Palajozoic Fossils, cited on page 262 of this paper. 



