XXXlll 



Of course these names are not founded on generic 

 characters, and, at best, can only be used to desig- 

 nate groups. 



3. Lithasia, B.aldeman. — This genus is recognized 

 by Messrs. Adams, but Mr. Reeve and Dr. Brot 

 confound its species with lo. Prof Haldeman first 

 proposed it as a subgenus of Anculosa. " Shell 

 heavy, having protuberances." This character ap- 

 plies only to certain species ; but the genus is now 

 recognized by American naturalists to include all the 

 species with the columella thickened above and 

 below. 



Prof Haldeman' s subgenus Angitrema is synony- 

 mous with, and has priority over, Glotella, Gray, 

 both adopting Melcuila annigera, Say, for their type. 

 As this subgenus really exhibits the highest devel- 

 opment of the species, I have concluded to adopt it 

 as a genus, using Llthasia as a subgenus for the 

 smaller, smooth forms. 



4. Strephohasis, Lea. 



5. Euryccelon, Lea. 



6. Goniohasis, Lea, May, 1862. — This genus will 

 retain Mr. Lea's name. Potadoma, Swainson, as 

 understood by Messrs. H. & A. Adams, embraces 

 certain species only. These gentlemen take some 

 species of this, Strephohasis and Pleurocera, to make 

 their JMegara, a subgenus of Gi/rotoma{ Schizostoma !) 



They make of the plicate group, Melasma, and of 

 the striate species they form Juga. These names 

 may be retained as sections of the genus, possessing 

 no really generic characters. 



7. Schlzosfoma, Lea, Dec, 1842. — Messrs. Adams, 

 Brot and Anthony, adopt Gyrotoma, Shuttleworth, 

 July 22, 1845, because Schizostoma was preoccu- 



Mr. Lea was himself of the same opmion, and 

 changed the name to Schizochihis (also preoccu- 

 pied). He subse(iuentl>- reclaimed the original name, 

 and I give him the genus as first published, having 



L. F. ^V. S. IV. 



