150 PROCEEDINGS OF THE ACADEMY OF [1890. 



SYNOPSIS OF AMERICAN CARBONIC CALYPTR^ID^. 



BY CHARLES R. KEYES. 



There has always been a considerable diversity of opinion as to 

 what term should really be applied to that paleozoic group of 

 gasteropodous shells commonly referred, by most American writers, 

 to Platyceras of Conrad. The described species of this group have 

 been variously and indifferently assigned to Capulus Montfort,^ 

 Fileopsis Lamarck,' Actita Fisher von Waldheim,^ Platyceras Con- 

 rad,* Acroculia Phillips,^ OHhonychiaHaW and some other genera. 

 Of these Capulus and Platyceras have become at last generally 

 adojDted ; the former having preference with most European, and 

 the latter with the majority of American authors. 



Generic Considerations. It may be premised here that the two 

 genera just mentioned are practically coextensive ; and since the 

 first has precedence — of more than thirty years — it should be used 

 instead of the second. Even if the group to which Conrad gave the 

 name Platyceras is a valid one it is very questionable whether the 

 term could stand, inasmuch as it has been preoccupied for three- 

 quarters of a century. It has long been known that Geoffrey in 

 1764 proposed for a genus of coleoptera the name Platyceras, a term 

 which was later employed by Latreille * and which continues to the 

 present day in good usage as originally proposed. Taking advantage 

 of this fact OEhlert '■' has recently revived Phillips' name Acroculia 

 for the Platyceras group of shells ; but this of course cannot i)e 

 adopted. 



As regards the actual generic characters of the various species, 

 their specific limitations, range of variation and the distribution in 

 time and space of the different varieties, greater confusion has, 



1 Conch. System., vol. II, p. 54. (1810.) 



2 Anim. sans Vertebr., t. VI, (2), p. 16. (1822.) 



3 Mem. de la Soc. imp. d. Naturalistes de Moscau, t. VI, p. 234. (1823.) 

 * Ann. Rep. N. Y. Gaol. Sur., p. 205. (1840.) 



5 Palte. Fobs. Cornwall, p. 93. (1841.) 



6 Rept. 4th Dist. N. Y., p. 172. (1843.) 

 "> Hist, abregee des Insectes, 1764. 



8 Precis des caracteres des Insectes, 1796. 



9 Bill, de la Soc. Geol. de France, (3), t. XI, p. 602. 



