1907.] NATURAL SCIENCES OF PHILADELPHIA. 220 



a new species of athleta and a note on the morphology of 

 athleta petrosa. 



by burnett smith. 



Introduction. ■ 



Though the present paper is intended primarily to show some of the 

 variations and mutations exhibited by one of our Eocene Volutoid 

 stocks, recent work in nomenclature has necessitated certain changes 

 of generic names, and therefore a brief explanation of these changes is 

 essential to a proper understanding of the forms here considered. 



In April, 1906, Dr. DalP called attention to the fact that the type of 

 Swainson's genus Volutilithes is not Voluta spinosa (which had been 

 previously accepted by most authors), but Voluta muricina Lam. A 

 similar observation was made by Mr. R. Bullen Newton^ in June, 1906. 

 Taking Voluta muricina as the type for the genus Volutilithes, it is 

 plainly evident that such forms as Voluta spinosa of Lamarck and 

 Vohita petrosa of Conrad must be furnished with a separate generic 

 designation and not included in the genus Volutilithes. In selecting a 

 name for these forms the writer has followed the suggestions of M. 

 Cossmann^ and revived Conrad's Athleta.* The type of Athleta is the 

 European Athleta rarispina. 



The forms studied in the present paper are all either specifically 

 identical with or else closely related to Conrad's Voluta petrosa, which 

 for so many years has been familiar to American palaeontologists as 

 Volutilithes petrosus. As the author has recently stated,^ the study 

 of large and carefully collected series from the Gulf States has con- 

 vinced him that the forms described as Athleta tuomeyi by Conrad are 

 nothing but races of his Voluta petrosa which have been subjected to 

 an unfavorable environment. "They are of one genetic stock, and the 

 differences can in no sense be regarded as generic; in fact they are not 

 even specific." 



' The Nautilus, "Xote on some Names in the Volutidte," p. 143. 

 ' "Note on Swainson's Genus Volutilithes," Proc. Maine. Soc. Land., June, 1906, 

 p. 100. 

 ' Revue Critique de Paleozoologie, p. 222, Oct., 1900. 



* "Svnopsis of the Genus Cassidula and of a proposed new genus Athleta," 

 Proc. Acad. Xat. Sri. Philn., Vol. VI, 1852-3. 



* The Xautihis. March, 1907, p. 131. 



U) 



