244 LITTORINID^. 



MEDORiA, Leach. Shell conical, solid, with elevated spire ; 

 peritreme dilated, anteriorly reflected ; inner lip thick, flattened ; 

 umbilical fissure obsolete. L. turrita, A. Ad. Japan. 



ERSiLiA, Monts. 1 sp. Mediterranean. 



HELA, Jeffreys. (Cithna, Jeffreys. ) Shell shaped like Lacuna, 

 with a similar operculum ; but it has no epidermis ; apex trun- 

 cated or flattened, and instead of an umbilical canal or groove 

 there is merely a narrow chink. Tentacles ciliated. L. tenella, 

 Jeffreys (Ixix, 33). Europe. 



Hela being preoccupied in another department of zoology 

 Jeffreys changed the name to Cithna — already used by Mr. A. 

 Adams for a somewhat similar shell. I restore the original 

 designation. Mr. Jeffreys being already honored with a generic 

 name in Conchology, I cannot pay him the compliment usually 

 tendered those who apply preoccupied names to new forms. 



STENOTis, A. Ad., 1863. Shell compressed, elongately ovate, 

 auriform ; spire short, acute ; whorls flattened, the last solute ; 

 aperture oblong, narrow behind, margin continuous, acute; 

 umbilicus patulous, its margin angulate. L. laxata, A. Ad. 

 Japan. 



LACUNARiA, Conrad. Ovate-conoid or subglobose, thin, with 

 delicate, close, revolving lines ; aperture entire, rounded or round- 

 ovate, angulated posteriorly, margins disunited ; columella 

 flattened, with a long groove descending from the umbilicus. 

 Eocene ; United States and France. L. Alabamensis, Whitfield 

 (Ixix, 34). 



spiRONEMA, Meek. (Callonema, Conrad.) Shell ovate ; whorls 

 rounded, and separated by a rather deep suture ; aperture ovate, 

 lip thin, continuous ; columella not thickened, perforated by a 

 very small umbilicus ; surface with revolving lines and furrows. 

 L. tenutlineata ^Meek and Hayden (Ixix, 35). Cretaceous ; U. S. 



LACUNELLA, Dcshayes. Shell oval, thin, pellucid, shining, 

 apex obtuse; aperture large, dilated, with thin, expanded 

 margin ; columella narrow, thin, concave, divided by a narrow 

 channel, scarcely perforate at the base. L. depressa^ Desh. 

 (Ixix, 36). Eocene; Paris basin. 



Cremnoconchus, Blanford. 



Syn. — Cremnobates, Blanf., preoccupied in fishes. 



Distr. — 3 sp. India, upon rocks wetted by fresh water. G. 

 Syhadrensis, Blanf. (Ixix, 31, 38). 



Shell perforate, turbinately globose, ribbed ; aperture subovate, 

 margin simple, columella scarcely callous. Operculum testaceous, 

 paucispiral. 



Animal small, having a short proboscis, two short tentacles 

 with eyes on swellings at their outer bases, foot short and 



