XXXVl 



SYNOPSIS OF GENERA OF STREPOMATIDiE. 

 I. Aperture produced into a more or less obvious canal in &ont. 

 Try pa n osto m o id Sect io n . 



1. Shell fusiform inflated on the periphery. 



Spire and canal produced ; columella without deposit 

 of nacre. — [Fig. 4.] Io, Lea. 



2. Shell conical, or oval, canal not so much produced. — 

 [Figs. 5, G.J Subgenus Pleurocera, Raf. 



Shell oval, or turbiniform, or fusiform, with a revolving 

 row of nodules on the periphery, canal short. Colu- 

 mella callously thickened above and below. 

 [Fig. 7.] Angitrema, Hald. 



Shell oval or oblong, smaller, either smooth or adorned 

 with nodules around the upper portion of the body 

 whorl. — [Fig. 8.] Subgenus Lithasia, Hald. 



Canal retrorse. — [Fig. 9.] Subgenus Strepiiobasis, Lea. 



Aperture merely angxilated in front, with no canal, and the columella 

 not twisted, frequently callously thickened above. 



Goniohasic Section. 



3. Shell obovate, heavy, nodulosely angled, aperture 

 ear-shaped ; columella oval, truncate. — [Figs. 10, 11.] 



EuRYCMiLON, Lea. 



II. 



Fig. 4. 



Fig. 5. 



Fig. C. 



Fig. 7. Fig. 8. 



Fig. 9. Fig. 10. 



Fig. n. 



