130 Marine Shells of the Western Coast of Florida 



terior concave; color brown or brownish. A smooth area about sum- 

 mit defined by a sutural hne indicates early spiral growth; below 

 this line are feeble radiating ribs. Basal aperture, somewhat oval, 

 margin finely crenulate; interior polished, brown; a white, funnel- 

 shaped internal septum below apex; animal adherent, shell free. 

 From about three to more than a hundred fathoms. 



Family CRKl'IDULIDAE 



The distribution of this family is world-wide throughout warm 

 seas at moderate depths. The adult mollusks are always affixed, 

 probably permanently; the shell is not attached and, like Anomia, 

 varies considerably in its form by reproducing any irregularities of 

 the surface it rests upon. 



The ova are deposited in grapelike bunches and retained be- 

 neath the shell until the larvae emerge. The animals of Crepidula 

 undergo a change of sex during the process of normal growth; in 

 young stages male attributes predominate, but as development pro- 

 ceeds this reversal of sex becomes complete. Groups of Crepidnla may 

 contain small male individuals, some in transitional stages and 

 others which have attained full reproductive maturity. 



Genus CREPIDULA Lamarck, 1799 

 Crepidula fornicita-^o (Linne) PI. 25, fig. 173 



Length to 40; width to 26 mm. Shell oval, oblique, with round- 

 ed margins and flattened spire; apex inclined to right, submarginal; 

 body whorl constitutes almost entire shell. Color varies through 

 shades of brown, frequently arranged in stripes or blotches; thin 

 yellowish epidermis. Surface shows only growth lines; interior pol- 

 ished, mottled purple-brown and white; internal horizontal dia- 

 phragm is concave, white, translucent, extending to middle of 

 aperture, its free margin slightly sinuous. Convexity and consequent 

 depth of shell are variable, some individuals are flattened, others 

 highly convex. Adherent to the outer, convex, surface of other 

 shells; sometimes in tiers of successively smaller individuals. 



From one to six fathoms. 



230 Lat., crepidula, a small sandal; fornicatus, vaulted. 



