244 LITTORINID A. 
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. lsp. 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 (lxix, 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. JL. lawata, 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 Statesand France. JL. 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. tenwilineata, Meek and Hayden (Ixix,35). Cretaceous; U.S. 
LACUNELLA, Deshayes. Shell oval, thin, pellucid, shining, 
apex obtuse; aperture large, dilated, with thin, expanded 
margin; columella rarrow, thin, concave, divided by a narrow 
channel, scarcely perforate at the base. L. depressa, Desh. 
(Ixix, 36). Kocene; Paris basin. 

CreMNoconcaus, Blanford. 
Syn.—Cremnobates, Blanf., preoccupied in fishes. 
Distr.—3 sp. India, upon rocks wetted by fresh water. C. 
Syhadrensis, Blanf. (1xix, 37, 38). 
Shell perforate, turbinately globose, ribbed ; aperture suboyvate, 
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 
