308 PALiEONTOLOGY OP NEW-YORK. 



Capili'S, Pileopsis, AcROciJLiA, and Platiceras. 



In the work entitled " Figures and Descriptions of the Palaeozoic Fossils 

 of Cornwal, Devon and West-Somerset," by Professor Phillips, published 

 in 1841, he has proposed the Genus Acroculia to include certain fossils 

 which had been referred to the Genus Pileopsis, and to which, he re- 

 marks, they " offer but slight analogy." His description is as follows : 



" Provisional character. Obliquely spiral ; the apex free, the aperture 

 " ample, without columella : a sinus in the right lip." 



This generic distinction has been acknowledged by some palaeontolo- 

 gists ; but, more recently, both Continental and English naturalists have 

 referred all these forms to Capclus or Pileopsis, which are regarded as 

 synonymous. 



Previous to the publication of the work of Professor Phillips cited 



above, Mr. Conrad, in his Report on the Palaeontology of New- York for 



1840 ( p. 205), proposed the generic name Platyceras, with the following 



remarks : 



" I propose to group in this genus the Pileopsis tubifer ( Soweuby ), P. vetusta 

 •' ( Sowerby), the J^erita haleotis ( Sowerby), and perhaps Bellerophon comuarietes. 

 " The shells are suboval or subglobose, with a small spire, the whorls of which are 

 " sometimes free and sometimes contiguous : the mouth is generally campanulate 

 " or expanded. I have not seen a species above the Silurian rocks, though they 

 " probably occur above them in Europe*, and they are never found in the Lower 

 " Silurian strata : they characterize the middle portion of the system." 



The generic description of Mr. Conrad is more comprehensive than 

 that of Professor Phillips, as it includes shells with the volutions free or 

 contiguous. Both authors, however, have designated among the typical 



• At the time this was written, the Hamilton and Chemung groups were regarded as a part of tlio 

 Silurian system by the New-York geologists, the Hamilton group being recognize*! as the equivalent of llio 

 Lndlow rocks of England; and we have yet seen no sufltcient reasons to regard it otherwise. Mr. Conrad, 

 in including the Bellerophon cornuarUtet in the Genus Plattcebas, must have regarded it as an un- 

 ■ymmetrical shell. 



