CYCLOPHORID.E. 



95 



ed. p. 69. — KusTF.R in Cliemn. ed. 2, p. 63, pi. xii, f. 6, 7, not of 

 Adams { = pallida'). 

 Amnicola luslrica, Haldeman, Mon. p. 16 (1844). — DeKay, N. Y. Moll. 87 

 (1843). 



Found also in Wisconsin and British America. 

 Fig. 189 is drawn from an authentic s})ecimen given by Mr. 

 Say to the Philadelphia Academy. 



Family CYCLOPHORID.E. 



Lingual membrane narrow, with seven rows of recurved, 

 hooked teeth. Head proboscidiform ; tentacles subulate ; 

 eyes on the outer side of the base of the tentacles. Foot 

 elongated. Operculum distinctly spiral, testaceous, carti- 

 laginous or horny ; whirls very numerous and sub-equal, or 

 few and rapidly increasing. Shell usually covered with a 

 horny epidermis ; aperture, for the most part, circular. 



Subfamily CYCLOSTOMIN.^. 



Operculum ovate, rarely subcircwlar, composed of a few gradu- 

 ally increasing whirls ; nucleus somewhat excentrical. 



Fig. 190. 



CHOIVDROPOMA, Pfr. 



Animal short, tentacles slender, enlarged at tips ; eyes promi- 

 nent, situated on a tubercle at the external 

 base of the tentacles. Proboscis 

 bifurcate. Operculum oval, sub- 

 cartilaginous, flat, with few, rap- 

 idly increasing whirls, and a nu- 

 cleus generally ver}' excentric. 

 Shell oblong-turreted, generally 

 truncated at tip, more rarely globosely conic ; aperture oval ; 



Animal of C. dentatum. 



Fig. 191. 



Operculum of 

 C. dentatum. 



