CHONDROPOMA. 191 



or more or less thickened, straight, expanded or widely 

 reflected. (Pfr.) 



The only species of the old genus Cydostoma found in 

 this country belongs to Chondropoma, and not to Cyclos- 

 toma, as restricted by Pfeiffer, as stated by Gould on p. 

 349. Other species are found in the West Indies. 



CHONDROPOMA DEXTATTJM SAY. .vol. ii. p. 348, pi. Ixii. Ixxv. fig. 24. 



Cydostoma dentatum SAT, (Binney's ed.) p. 29. 



Ckondropoma dentatum PFEIFFER, Mon. Pneum. Viv. i. 286; ii. 140; Malak. Bl- 



1856, p. 132. 

 GRAY and PFEIFFER, Brit. Mus. Phan. 203. 



A view of the animal, twice its natural size, is given on 

 pi. 75, fig. 24. 



It will be noticed that I have omitted from the synony- 

 my the West Indian species C. lineolatum, crenulatum, 

 Auberianum, and huiulatum. It is at present impossible 

 to speak with certainty about their identity with dentatum. 

 Poey removes it from his Cuban Catalogue, (Mem. i. o93.) 



It is worthy of note that Orbigny describes Auberianum 

 as having equal transverse and longitudinal striae. A 

 reference to the enlarged figure of the surface shows a 

 very different case in dentatum. 



SPURIOUS SPECIES. 



Cydostoma Cincinnatensis Lea and DeKay, and 0. lapidaria Say 



Linsley, and Kirtland, are species of Amnieola. 

 Cydostoma marginalis Kirtland, (Ohio Rep.) and C. marginata 



Say, are species of Bulimus. 

 Cydostoma tricarinata Say is a Valvata. 



FAMILY HELICINACEA. 



Operculum without any vestige of a spiral form, testa- 

 ceous, heavy or horny, thin, and furnishing no reliable 



