124 AMERICAN JOURNAL 



Synopsis of Genera of StrejJomatidse. 



1. Aperture produced into a more or less obvious canal in front. 

 Tr ypawjstomoid Section. 



i. Shell fusiform inflated on the periphery. 

 Spire and canal produced ; columella without deposit of 

 nacre. lo, Lea. 



(Plate 17, fig. l.J) 



Shell conical; or oval, canal not so much produced. 



Subgenus Pleueocera, Raf. 

 (Plate 17, figs. 2, 8.} 



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

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

 mella callously thickened above and below. 



Angitrema, Ilald. 

 (Plate 17, fig. 4.) 



Shell oval or oblong, smaller, either smooth or adorned 

 with nodules jiround the upper portion of the body 

 whorl. Subgenus Lithasia, Hakl. 



(Plate 17, fig. 5.) 



Canal retrorse. Subgenus Strephobasis, Lea. 



(Plate 17, fig. 6. J) 



2. Aperture merely angulated in front, with no canal, and the 

 the columella not twisted, frequently callously thickened 

 above. Ooniohasic Section. 



3. Shell obovate, heavy, nodulosely angled, aperture ear- 

 shaped ; columella oval, truncate. EuRYC^LON, Lea. 



(Plate 17, figs. 7, 8.) 



4. Shell heavy, oval, truncate, oblong, or turrited ; aper- 

 ture entire above. Goxiobasis, Lea. 



(Plate 17, figs. 9, 10. J 



o. Aperture with asutural, pleurotomose slit above. 



ScHizosTOMA, Lea. 

 (Platen, fig. 11. J 



6. Lip slit in the middle. Meseschiza, Lea. 



3. Aperture entire and rounded in front. 



7. Shell oval, heavy ; columella callously thickened 

 above. Anculosa, Say, 



(Plate 17, fig. 12.; 



