GASTEROPODS 



369 



GENUS Sigaretus 



A very interesting species of this genus occurs on the east 

 coast, sparingly in New Jersey, but very abundantly south of 

 Hatteras. Sigaretus is a modified Natica. The spire is flattened 

 and minute. The body-whorl, being greatly expanded, gives a 

 wide, flaring, oblique aperture. The shell is ear-shaped and white, 

 with fine revolving lines. There is no umbilicus. The operculum 

 is small and rudimentary. The animal is large, with an enormous 

 foot and greatly developed propodium, and is a sand-dweller. 

 The common east-coast form is S. perspectivus. (Plate LXVIII.) 



FAMILY CAPULIDJE 



GENUS Crepidula 



C. fornicata. All collectors of tnollusks on the Atlantic coast sooner 

 or later encounter this exceedingly common species adhering to oyster- 

 shells or scallops, and often to other large live shells. 

 It is cast upon the beach along the entire length 

 of the Atlantic coast. The shell is obliquely oval, 

 dull whitish in color, and either smooth or rough 

 or even ribbed, according to the nature of the sur- 

 face to which it clings. The spire is almost entirely 

 suppressed, the little inconspicuous apex being 

 turned to one side and closely pressed down against 

 the body of the shell. When looking into the in- 

 terior of the shell one is reminded of a boat, for the 

 upper portion of the aperture is covered by a 

 horizontal shelly partition, called the diaphragm, 

 a space being left below which would correspond 



to the forecastle of a ship. The "stern" is round, 

 and the " bow " is suggestively pointed. 



C. plana. In this species the shell is white and flat, 

 or slightly concave. Although it is pointed at the ' ' bow " 

 end and square at the " stern," the nautical resemblance 

 stops there, because, being flat, there are no swelling 

 sides and bow. The diaphragm is about one half the 

 length of the shell, convex, shining, white, and trans- 

 lucent. C. plana lives generally within the aperture of 

 large dead shells. It has a wide range, from Maine to 

 Florida. 



C. aculeata. A common Floridian species which has 

 a remarkable range, being found in nearly all the tropical and semi- 

 tropical waters of the world. It is smaller than C. formcata, is reddish- 

 brown with a white diaphragm, and has several radiating ribs on the 

 back, which are inclined to be nodulous. (Plate LXVIII. } 



24 



Crepidula fornicata. 



Crepidula plana. 



