442 MARINE INVERTEBRATES 



it from all other shells of our coast of similar size, is the coarse, wrinkled 

 epidermis of black to chestnut color. The shell is very suggestive of a 

 large, overgrown Astarte. Length three and a half inches; height 

 three inches. It is found of all sizes, down to one fourth of an inch in 

 diameter, upon muddy stations in moderately deep water near the 

 mouths of rivers ; but the surest way to get it is to search the beach 

 after a hard onshore gale. 



FAMILY LUCINIDJE 



This family finds its metropolis in warmer waters, and the best 

 representatives of it must be sought for upon the Floridian 

 beaches or in the shallow bays of that sandy coast. A long ver- 

 miform foot is a characteristic of the animal, as is also the fact 

 that at times there is only a single gill upon each side of 

 the body. In some of the Lucinidce, more so than in most other 

 pelecypods, the chief function of the gills is to furnish a brood 

 ing-place for the thousands of ova which the creatures generate 

 Sometimes a Lucina will be captured with the gills swollen out of 

 all proportion, and literally stuffed with tiny, microscopic eggs, 

 At such times the gills lose all semblance of branchial organs. 

 The shells are orbicular/with depressed small umbones, a distinct 

 lunule, a semi-external ligament, two cardinal teeth, and laterals 

 (a variable feature). There is no pallial sinus. The color is 

 white, and the outlines are rounded. 



GENUS Lucina 



L. tigrina. The largest of the group, measuring three inches across 

 and nearly the same in height. It is flatly convex and radially ribbed 

 by a great number of costse which are crossed and decussated through- 

 out with concentric ridges. The color is white. This fine shell lives 

 only in southern Florida and is abundant in shallow water on sandy sta- 

 tions. (Plate LXXX.) 



L. floridana. One of the most abundant bivalves in Florida, often 

 cast in thousands upon the beaches. It lives in shallow protected 

 waters and upon sand-flats which are partly exposed at low tide. It 

 has the usual round outlines of the genus, with exceedingly small um- 

 bones, directed forward, and a smooth surface, save for fine growth- 

 lines of a light straw-color. The shell is pure white. Diameter about 

 one inch. (Plate LXXX.) 



L. pennsylvanica. A species often associated with the last, but about 

 twice as large. Its thin but tough epidermis clings to the shell in raised 

 concentric lines, giving it a circularly ribbed appearance. The most 

 prominent feature of this species is a depressed line upon either valve 

 extending obliquely from the umbones to the posterior ventral margin, 



