THE MOLLUSCA 



979 



13 (14) Shell ovate-oblong; spire produced, pointed; outer lip thickened, 

 sometimes with one denticle on the callus. 



Subgenus Ovatella Bivona. 



A single European species, Melampus bidentata Mont., (Fig. 1411; X 2O, intro- 

 duced on the coast of New England. " The shell, except for its smoother epidermis 

 and obsolete parietal denticle, is almost exactly like the lighter-colored forms 

 of Tralia mysotis, a fact which has led to much confusion" (Dall.). In living 

 examples, this species is easily distinguished by the transversely divided foot. 

 Fig. 1411. 



14 (is) Shell elongated, solid, rounded to a point at both ends; outer lip 

 Urate within Subgenus Detracia Gray. 



Asingle species, Melampus bulloides Mont., (Fig. 1412; X 25), is found along 

 the Florida coast and keys. 



Fig. 1412. 



15 (12) Shell small, thin, subfusiform; spire elevated; columella twisted to 

 form one strong, spiral ridge entering the volutions; outer 

 lip thin, sharp, without internal lirae, thickening or denticu- 

 lations Subgenus Sayella Dall. 



Only two minute species are known, both of which occur on the Florida coast. 

 Example, Melampus hemphUli Dall. (Fig. 1413; X 5.) 



Fig. I4I3- 



16 (10, 11) Shell small, sinistral, elongate; lip sUghtly thickened, smooth 

 within Blauneria Shuttleworth. 



A single species, B. heterocUta Mont., (Fig. I4r4; X i\), occurs on the Florida 

 coast. It is easily distinguished by its sinistral shape. 



Fig. 1414, 



17 (3, 22) Animals marine or semi-amphibious, living on rocks where they are 



immersed at high tide. Head without tentacles. ... 18 



18 (21) Shell patelliform, with a subcentral apex. Animal with a jaw and 



both lung and gill Family Siphonarhdae. 



Only one genus Siphonaria Sowerby . . 19 



10 (20) Shell solid, porcellanous; surface with more or less elevated ribs ex- 

 ^^^^ tending to the margin Subgenus Siphonaria s.s. 



Two species only, found on the east coast of Florida. Example, S. alter- 

 nata Say, (Fig. 1415)- 



Fio. 1415- 



