122 Dentition of Pulmonate MollusJcs. 



Liostracus alter nans, Beck. Islands in the Bay uf Panama. 

 Mr. McNeil. 



Jaw as usual iu the genus, 52 ribs. 

 Lingual membrane as in last species. 



Liostracus Marielinus, Poey. 

 See Terr. Moll., Y. 



Mesembrinus primularis, Rve. Northern Peru. Prof. Orton. 



Jaw as usual in the genus. 



Lingual membrane (PI. XII, rig. G) as in last species, but there is only 

 one cutting point in the central tooth. 



Mesembrinus pallidior, Sowb. 



See Terr. Moll., V. 



Lingual membrane as in the following, not as in last species. 



Mesembrinus chrysalis, Pfr. Martinique. Gov. Eawson. 



Jaw of the type common in Bulimulus, Cylindrdla, etc., arcuate, low ; ends 

 blunt ; thin, transparent ; with eighteen narrow, separated ribs ; a trans- 

 verse central line of reinforcement. Attached to the upper margin is a strong 

 triangular membrane of the same consistence and material as the jaw itself, 

 and equally resisting the action of potash, so as readily to be mistaken for 

 the accessory plate of the Succinece. (Pl.^XV, tig. Q.) 



Lingual membrane (PI. XIV, fig. G) as usual in the Helicince. Centrals 

 about as broad as long, tricuspid, and median cusp short and stout, its short 

 point not extending to the base of the plate. Laterals like the centrals, but 

 bicuspid. Marginals wide, low, with one inner, long, blunt, stout, oblique 

 denticle, and one or two short, blunt side denticles. 



Thaumastus immaculatus, Ad. Jamaica. Mr. Gloyne. 

 Jaw as usual in Bulimulus ; over 36 ribs. 



Lingual membrane (PI. XII, fig. H) as in Bui. chrysalis ; central teeth with 

 three cutting points. 



. Mormus membranaceus, Phil. Brazil. J. G. Anthony. 

 Jaw as usual ; with about 24 ribs. 

 Lingual membrane as in Bui. chrysalis. 



Mormus laticinctus, Guppy. Dominica. Mr. Guppy. 

 Jaw not examined. 



