87 
On the surface of internal casts we observe the impressions of the 
umhonal divergent ridges, the short “auricular crnrm,’” hut the chondro- 
phores and “auricular tu])ercles”" are preserved in neithe]* * valve, nor the 
transverse auricle furrows of the left valve. There is no trace whatever of 
cardinal crenulations or resilifers. 
W e are quite iinahle to separate these shells from EntoUum aviculatam, 
Swallow, sp., as figured by Meelc. Any attempt to unravel the intricate 
syiionomy of this species is he\U)nd us, and, without a complete suite of 
American and European specimens of Pernopecten and Entoliiini, such an 
attempt would he both futile and unprofitable. We may remark, however, that 
we believe time and investigation will prove some, at least, of the shells 
described by one of us as Pecten or EntoUum Sowerhyi, McCoy^ [non Nyst), 
if not the species in chief also, to be identical with E. aviculatum. The 
trivial features of stronger concentric markings, auricles more pointed or 
elevated, suggested by Mr, Meek as a means of separation between Entolium 
Soioerhyi and PJ. aviculatum, can hardly bo looked upon as more than varietal. 
Even in E. Soioerhyi itself mucli variation exists in these characters. 
The forms previously referred to Entolium Soioerhyi, and possil)ly 
identical with E. aviculatum, are; — P. (Amussium) Soioerhyi, Eth. fil.,^ and 
Entolium Soioerhyi, Etli. til."’ 
In the event of the American and British shells, as here indicated, 
proving identical, McCoy’s name undoubtedly has precedence, but NysC 
described a Pecten Soioerhyi nwicviov to McCoy, and under strict nomenclature 
rules that of the latter author becomes a synonym. To avoid any complication 
in such a contingency, we tliink it Avill be better to adopt D’Orbigny’s name 
of Pecten hathus' following Professor de Koninck’s lead.® 
It is also within the range of possibility that Pecten valdaicus, Keys, 
and de Vern.,® and other figures of Pecten Soioerhyi^^ by one of us, may be 
* Verrill — Trans. Connecticut Acad. Arts & Sci., 1899, X, Pt. 1, p. 51. 
2 Verrill — Ibid. 
^ McCoy — Synop. Carb. Lime. Foss. Ireland, 1841, p. 100. 
^Etheridge, Junr. — Geol. Mag., 1S77, IV (2), t. 12, f. 1-3. 
° Etheridge, Junr. — Ann. Mas. Nat. Hist., 1878, II (5), t. 1, I. 3-5. 
“Nyst — Descrip. Coqu. Polyp. Foss. Terr. Tert. Belgique, 1813, p. 293. 
' D’Orbigny — Prod. Pal., 1850, I, p. 139. 
* Da Koninck — Recb. Anim. Foss. Carb. Bleiberg, 1873, p. 94. 
“ Keyserling and De Verneuil — ^Murchison’s Geol. Russia in Europe, 1815, II, p. 328, t. 27, i. 9. 
^“Etheridge, Junr, — O-eol. Mag., 1874, I (2), t. 13, f. 1-3 
