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 s^Qcits, Melamptis bidenlata Mont., (Fig. 141 1; X 2 j), 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 tnysotis, 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 (15) Shell elongated, solid, rounded to a point at both ends; outer lip 

 Urate within Subgenus Dctracia Gray. 



A single species, Melampus buUoides Mont., (Fig. 1412; X 2,), is found along 

 the Florida coast and keys. 



Fig. 141 2. 



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 hemphilli Dall. (Fig. 1413; X 5.) 



Fig. 1413- 



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

 within Blauneria Shuttleworth. 



A single species, 5. heteroclita Mont., (Fig. 1414; X 3 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 SiPHONARnDAE. 



Only one genus Siphonaria Sowerby . . 19 



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

 l^®k tending to the margin Subgenus Siphonaria s.s. 



Two species only, found on the east coast of Florida, Example, 5. dter- 

 y<^ nata Say, (Fig. 1415)- 



Fig. 1415. 



