96 American Seashells 



Puncturella cucullata Gould Hooded Puncturella 



Figure 30a, b 



Alaska to La Paz, Mexico. 



% to I inch in length, moderately strong. Apex small, elevated and 

 hooked over toward the anterior end. Behind it is a small, elongate slit pene- 

 trating through the shell. Internally the slit is separated from the apex by a 

 calcareous, convex shelf. Exterior with 14 to 23 major ribs and with i to 5 

 smaller radial ribs between the main ones. The fewer the ribs, the stronger 

 they are. Shell dull-gray externally, glossy-white inside. The border is cren- 

 ulated. Found at low tide in Alaska and dredged from 20 to 75 fathoms off 

 southern California. 



Puncturella galeata Gould Helmet Puncturella 



Figure 30c 



Aleutian Islands to Redondo Beach, California. 



% to % inch in length, similar to cucullata, but with an almost smooth 

 basal edge; with numerous, much finer radial ribs, and with the internal shelf 

 behind the slit reinforced by a second, straight shelf. Commonly dredged in 

 mud from 10 to 75 fathoms. 



Subfainily DIODORINAE 

 Genus Diodora Gray 1821 



Keyhole Limpets with the internal callus of the hole truncated and fre- 

 quently minutely excavated behind; shell with its basal margin never raised 

 at the ends. Central tooth of the radula wide. Compare with Fissurella. 

 Diadora is a misspelling. 



Diodora cayetiensis Lamarck Cayenne Keyhole Limpet 



Plate 17m 

 Virginia to south half of Florida and to Brazil. 



I to 2 inches in maximum diameter. Orifice just in front of and slightly 

 lower than the apex. Many radial ribs with each fourth one larger. Color 

 variable from whitish, pinkish to dark gray. Interior white or bluish gray. 

 Just behind the callus of the orifice on the inside there is a deep pit. D. listeri 

 is much more coarsely sculptured. A common intertidal to moderately deep 

 water species. It was named by Thomas Say one month after Lamarck's 

 description as D. alterjiata. 



Diodora listeri Orbigny Lister's Keyhole Limpet 



Plate 17I 



South half of Florida and the West Indies. 



