58 Marine Shells of the Western Coast of Florida 



umbo higher than its fellow; inequilateral, prolonged, narrowed, 

 truncated and open posteriorly; umbos minute, pointed, in contact; 

 dorsal margin concave behind umbos; shell surface shows incremental 

 lines, with radiate wrinkles and marginal folds of the epidermis; hinge 

 without teeth, a small submarginal groove for ligament and litho- 

 desma posterior to umbos; interior pearly, two muscular impressions, 

 indistinct pallial line; delicate byssus. 



Found in muddy bottom in shallow water. 



Lyonsia beaiia"'' d'Orbigny PI. 9, fig. 51 



Alt., 8; length, 23; diam., 9 mm. Shell pearly, smooth; brown- 

 ish, radiately striate epidermis; shape irregular, inequivalve, inequi- 

 lateral, prolonged and widened behind; posterior margin rounded, 

 gaping; umbos anterior, small, close; hinge and interior typical. 



Found in deeper water than L. jloridana, frequently in sponge or 

 attached by delicate byssal threads to other shells. 



Family CUSPID VKIIDAE 



Most members of the family Cuspidariidae are inhabitants of 

 profound depths; they are native to all seas, but are seldom seen 

 except with dredged material. The shells are small, white, with thin 

 epidermis; pyriform; slightly mequivalve, left valve larger and of 

 greater convexity; inequilateral, round and inflated anteriorly, 

 posterior portion beaked, gaping. There is an external linear ligament, 

 and an internal cartilage placed in a small spoon-shaped fossette. 

 Hinge teeth variable; two muscle scars; pallial line has small sinus. 



Genus CUSPIDARIA Nardo, 1840 



Subgenus CAUDIOMYA A. Adams, 1864 



Cuspldariu"" ^eiiumi (Verrill and Bush) PI. 9, fig. 52 



Alt., 3.5; length, 6 mm. Shell fragile, thin, white; smooth epider- 

 mis; delicate concentric growth lines; four radiate ribs — one almost in 

 center of shell, three posterior to center; rounded ventral margin, 

 angulated termination of ribs; posterior end of shell prolonged; right 

 valve has one lateral tooth. 



Dredged at one to two fathoms in blue mud. 



^^ A. S., bean, from a Gothic word meaning to puff up. 

 ®^ Lat., cuspid'ts, pointed end; gemma, a bud. 



