GASTROPODA 539 



lengthened snout; the animal adlieres by means of the broad foot to 



stones and shells, and does not move about : 7 genera and 160 species. 



Key to the genera of Capulidae here described: 



a, Shell conical : partition cup-shaped 1. Crucibulum 



Wj Shell with a slight spiral; partition more or less horizontal. . . .2. Crepidula 



1. Crucibulum Schumacher. Shell, conical and not 

 spiral, with the apex directed posteriorly; shelf more or 

 less cup-shaped, attached to the inner wall near the apex, 

 on one side: cosmopolitan. 



C. striatum (Say) (Fig. 835). Cup-and-saucer limpet. 

 Shell solid, with numerous elevated radiating lines; aper- jap*xcii;i>-*' 

 ture circular; white or yellowish in color; 12 mm. in 

 height and 20 mm. in diameter : Florida to Bay of Fundy ; crucihuium 

 in 2 to 189 fathoms; common in shallow water towards fverrni?. 

 the north. 



2. Crepidula* Lamarck. Shell oval, boat-shaped or flat, with the 

 inconspicuous spire at the hinder end; shelf an internal regular plate 

 in the hinder half of the shell: 50 species, in all the warmer seas; 

 attached to shells, seaweed, etc. 



Key to the species of Crepidula here described: 



«! Shell convex. 



bi Shell up to 45 mm. long ; shelf white C. fobnicata 



6a Shell 12 mm. long or less ; shelf brown C. convexa 



«a Shell flat C. plana 



'"'"^^^ll^fj/ C. fornicata (L.) (Fig. 836). Shell convex, with 



:t^':-:.w^ one side more curved than the other; color whitish or 



Fig. 836 Crepid- brownish ; shelf concave, white ; lengih 45 mm. ; width 



"^" Ve?Si)f "" 33 mm. ; height 15 mm. : Nova Scotia to South America, 

 in shallow water, very abundant ; Europe. 

 C. convexa Say. Shell very convex, the short side being nearly 



vertical; color whitish or brownish; shelf deep-seated, convex, brown 



in color, with a white edge ; length 12 mm. ; width 8 mm. ; height 4 mm. : 



Nova Scotia to Florida, in shallow water; not so abundant as the above; 



Pacific coast. 



C. plana Say. Shell flat or concave, with a minute apex; white and 



polished inside ; length 40 mm. ; width 25 mm. : Maine to Texas ; common 



in shells from low-water mark to 487 fathoms. 



Family 3. LITTORINIDAE. 



Shell spiral and conical; lip not notched; aperture round, interior 



not pearly; operculum horny and spiral; head projecting, tentacles 



♦ See "The Embryology of Crepidula," by E. G. Conklin, Jour. Morpb., Vol. 13, 

 1897. 



