296 littoeinidj:. 



to New York, and from Missouri to Michigan. It is also found in 

 the postpleioccne of the Mississippi River bluffs. 

 Housatonic River (^Linsley). 



Family LITTORINID^, Geay. 



Shell spiral, turljinatcd or depressed ; aperture simple in front, 

 never pearly within. 



Genus SKCrVEA, Fleming. 1828. 



Shell minute, discoidal ; whorls few, and destitute of spines ; 

 aperture dilated ; operculum horny. 



Skenea planorbis. 



Tig. 189. 



Shell minute, discoidal, concavely umbilicated beneath, horn colored, whorls 

 three, mouth expanded. 



Turbo planorbis, 0. Fabricius, Fauna Gr. 394. 



Skenta phuiorbis, Fokbes and Hanley, &c. ; Stimpson, Shells of New England, 35; 



Check Lists, 4. 

 Skenea serpuloid(S, of American not European authors, Gould, Inv. 1st clI. p. 247, fig. 189. 



Shell minute, flat, slightly convex above, and broadly concave be- 

 low, forming a deep umbilicus, which displays all the wliorls within; 

 whorls three, smooth, a little depressed, light horn color ; 

 '° ' ■ apex scarcely elevated ; suture channelled ; aperture turn- 



ing downwards, circular, somewhat trumpet-shaped, in con- 

 /^T^ tact with, but not eml)raciiig any part of, the preceding 

 ^--^ whorl ; lip sliarp, and receding so as to form an acute gap 

 ^orbi'J'' ^^ ^^ joins the preceding whorl ; operculum luji-ny, multi- 



s])iral, the apex central. Breadth, one twentieth of an inch ; 

 height, one thirtieth of an inch. 



Clings to stones lying about low-water mark. I have found it 

 occasionally, but Professor Adams has found it in great numbers 

 along the southwestern shore of East Boston. Nova Scotia ( Wil- 

 lis) ; Cape Cod, northward (^Stimpson). 



Oeiius KISSOELLA, Gray. 1847. 



Shell thin, spiral, conical, or sub-globose, transparent ; aperture 

 ovate, rounded and simple in front, peristome thin, entire. 



