GASTEROPODS 351 



As has already been remarked, shell-bearing opisthobranchs 

 are not abundantly represented in number of species in North 

 American waters. South of Cape Cod, in muddy bays and well- 

 sheltered places, the little shell, Haminea solitaria, may, however, 

 often be found in considerable numbers. 



.He solitaria. Like all external opisthobranch tests, the shell of this 

 species is thin and fragile, and would appear to be of small importance 

 to the creature it only partially protects. It is devoid of spire, is 

 shining bluish- white, sometimes brownish in color, and is 

 marked with revolving grooves, which, being cut across by 

 irregular growth-lines, give its surface a faintly decussated 

 appearance. The aperture is as long as the shell ; the colu- 

 mella is incurved. This little species is especially abundant 

 in shallow water about Vineyard Sound and in Peconic Bay. 



GENUS Sulla 



B. occidentalis. This species, which is found in the waters of 

 Florida on all sandy beaches, is a relative of the Northern species just 

 described. The shell is larger than that of Haminea solitaria, and has 

 a color-pattern of mottled or clouded reddish-brown on a white foun- 

 dation. There is no spire ; there is a pit in place of an apex ; and the 

 aperture extends the full length of the shell. To the naked eye the surface 

 appears smooth and shining. It is an exceedingly variable species, 

 occurring ah 1 through the West Indies, but not north of Florida. The 

 shores of the keys along the west coast of Florida are often strewn with 

 these shells after storms. The animal, like all the shell-bearing opistho- 

 branchs, is very large as compared with the shell, and the large mantle 

 folds recurve upward, almost completely hiding the shell from view. 

 (Plate LXV.) 



B. nebulosa. This is one of the largest and finest species of the 

 family Bullidce. It is found on the coast of California south of San 

 Francisco. The shell is much larger than that of either of the Atlantic 

 species mentioned above, but very closely resembles them in outline, 

 although it is built upon a more generous plan and is more richly 

 painted. It is brownish, mottled with white and yellow patches, and is 

 very suggestive of certain kinds of birds' eggs. The animals have a 

 greatly extended mantle which almost completely envelops the shell. 

 The foot is extremely large, with great wing-like developments upon 

 each side, called parapodia. Some species of Sulla have been seen to 

 swim by means of the lazy napping of the parapodia. (Plate LXV.) 



SEA-HARES 



Closely allied to these outer-shell-bearing opisthobranchs is a 

 large and important group of tectibranchs, known as "sea- 



