Occasional Papers of the' Museum of Zoology 41 



Chondropomixae 

 Genus Tudora 



Tudora Gray (1850; Brit. Mus. Cat. Cvclopli., 48); monotvpe Cyclos- 

 toma simile "Grav" Sowerby. 



Shell: ovate conic to elongate ovate. Sculpture: exceed- 

 ingly variable, but the growth ribs are not tufted at the suture 

 nor is the latter channeled. Embryonic whorls: II/2, not 

 distinctly limited; cream to dark horn-colored, commonly 

 darker below; practically smooth, but irregularly and very 

 minutely wrinkled. Peristome : simplex, sharp ; incomplete or 

 continuous; not abruptly reflected. 



Operculum: perimeter channeled; chondroid plate rela- 

 tively thin; calcareous portion consists of vertical growth- 

 lamellae, which are often cemented together by interstitial 

 material, and which coalesce at their distal edges to form a 

 calcareous plate; the last is almost parallel to the chondroid 

 one, and is marked externally by rather weak growth-wrinkles. 



Radula : central and inner lateral with hea^T> triangular 

 bases, each with a single, heavy cusp ; outer lateral with rec- 

 tangular base and markedly reflected tip, which bears about 

 five aculeate to spatulate cusps; marginal with numerous, 

 recurved, lanceolate cusps, which fill more than half of the 

 entire distal edge, outer uncusped portion abruptly sloping 

 down to relatively narrow base. 



Although the radulae of the Chondropominae are simple 

 and rather uniform in structure throughout the subfamily, 

 they do show characters of considerable systematic value, 

 which I hope to present in a future paper. Amongst many 

 others, I have examined the radulae of several of the species 

 that belong to the Jamaican, Mexican and Central American 

 group, usually known as Colobostylus, and believe it to be 

 quite distinct from Tudora. In addition, the simplex, slightly 

 expanded peristome of the latter genus is quite different from 

 the duplex, thickened condition in the northern group, and 

 was utilized for their separation by most of the earlier writers. 

 I have not been able to examine the radula of any of the 

 Cuban and Haitian species, which include typical Licina, but 



