H 



38 PROCEEDINGS OF THE ACADEMY OF [Vol. LXXIV 



TT. More (9) marginals bicuspid, close- 

 ranked; shell usually with upper sinus on 

 aperture; Mexico and Guatemala 



Subgenus Schasicheila. 

 <+. A-central unicuspid; B-central with 3 heavy 

 cusps; comb-lateral tricuspid; inner 10 mar- 

 ginals unicuspid; shell small, slightly like 



Schasicheila s. s. in shape Stoastoma. 



AA. Capituliform complex consisting of a mushroom-shaped T. 

 lateral and a reduced accessory plate; many unicuspid 



marginals Subfamily Vianinae, new. 



B. Marginals with sharp-pointed blades; T-lateral with stalk 

 as long as width of tooth, which is considerably smaller 

 than central field of radula; R-central triangular-ovoid 



to broadly elliptic Eutrochatella. 



C. All paired centrals with at least three well-developed, 

 cusps; T-lateral with cusps on margin; shells smallish 

 quite smooth and elongate 



Subgenus Troschelviana, new. 



D. T-lateral with well-developed cusps on inner portion 

 of margin; shell smallish, quite smooth and elongate: 



Section Troschelviana. 

 DD. T-lateral with a few cusps towards outer portion 

 of margin: shell more conoid in shape 



Section Cubaviana, new. 

 CC. At least A-central without well-developed cusps; 

 T-lateral without cusps on margin; shell with spiral 

 sculpture.. 



E. B-central with 3 quite well-marked cusps; T-lateral 



with horny thickenings near margin which give the 

 tooth a wavy appearance; small species 



Subgenus Pyrgodomus. 

 EE. Both A and B centrals without well-marked cusps; 

 T-lateral without sign of cusps; larger species. 

 F. R-central broadly elliptic; operculum with nucleus 

 near columellar margin and almost linear; de- 

 pressed pagoda-shaped shell 



Subgenus Priotrochatella. 

 IT. R-central narrowly ovoid to circular; operculum 

 with nucleus nearer center 

 Sul. genus Eutrochatella; Sections Ustronia, 



Excavata, Eutrochatella. 

 BB. Marginals with tips more rounded; T-lateral with short, 

 -tout stalk, and broad, semicircular cutting edge, so 

 ih.it entire tooth is almost or fully as large as the central 

 field of the radula (7 teeth); R-central more or less 

 shield-shaped with scallops on lateral margins; paired 

 centrals and T-lateral without cusps. 



