90 PALEONTOLOGY OF NEW YORK. 



group ; A. Cora, Hall, of the Hamilton group ; A. vi'tata* Hall, of the Cornifer- 

 OU8 limestone and Hamilton group; A. Angelica, Hall, of the Chemung group; 

 A. lamellosa, Li'-veilU', of the Waverly and Keokuk groups ; A. incrassata. Hall, 

 of the Burlington limestone, and A. Hannibalmsis, Swallow, of the Choteau 

 limestone. 



Subgenus CLIOTHYRIS, King. 1850. 



This name was introduced by Professor Phill[P8, in 1841,f as a substitute for 

 Dalman's term Atrypa, which this author did not regard as appropriate. The 

 term wa.s not subsequently used by him, nor was any typical species mentioned, 

 so that in its original application the term has no meaning. Subsequently, and 

 perhaps unfortunately, Professor William King revived the name, J giving a 

 careful diagnosis and specifying as his type of the genus, Atrypa pecUnifera, J. 

 de C. Sowerby. 



His description was : " Generally lenticular in form ; minutely punctured ; 

 with variously characterised projecting laminae of growth ; Spirab pectinated ; 

 Dental plates large and separated ; Crural base perforated ; Foramen situated at 

 the point of the umbone, and open inferiorly by the fissure." 



At this date the genus Athyris was not closely restricted or well understood. 

 Kino followed McCoy in regarding Terebratula concentrica, von Buch, as its type, 

 and demonstrated, though imperfectly, the existence of a process connecting 

 the spiral coils of the shell. 



Atri/pa pedinifera is a Permian species which varies from the structure in the 

 typical division of Athyris in the following respects : The surface ornamenta- 

 tion consists of broad, thin, lamellar expansions which are divided almost, 

 and sometimes quite to their bases, into long, flat spinules; hinge-plate nar- 

 row and rather acutely triangular ; the primary lamellae are attached to the 



* These three species are pretty constant in their differences, the first being transverse, squamous forms, 

 the others more orbicular and retaining but traces of the laminae. The species present vaiiations which 

 are included by European palffiontologiats within the limits of Athyris conctntrica, von Buch. 



t Palteozoic Foiwils of Cornwall, Devon and West Somerset, p. 65. 



X The Permian Foeails of England, p. 137. 



