418 



American Seas be Us 



2 to 3 inches in length, similar to elegans, but having more and finer 

 concentric ridges (about 50 per inch in adults), and not so circular. Com- 

 monly washed ashore in perfect condition after storms along the Carolina 

 coasts and middle western Florida. 



Subjamily EMMINAE 



Very small shells, with marginal grooves and denticles simulating lateral 

 teeth. Inner ventral margins crenulate. 



Figure 84. Amethyst Gem Clam, a and b, Gejnma gevnna Totten, % inch; c to 

 e, the form purpurea Lea, % inch. 



Genus Geimna Deshayes 1853 



Shell the size and shape of a split-pea; lunule large, faintly impressed; no 

 escutcheon; 2 large teeth in the left valve with a large, median socket between 

 the two. A very thin ridge which might be termed a tooth occurs posteriorly 

 beneath the ligament. 3 teeth in right valve. Pallial sinus small and triangular. 

 The shells of the brooded young may be found inside some females. 



Gemma gemma Totten Amethyst Gem Clam 



Plate 38k; figure 84 



Nova Scotia to Florida, Texas and the Bahamas. Puget Sound, Wash- 

 ington (introduced). 

 % inch in length, subtrigonal, moderately inflated and rather thin-shelled. 

 Exterior polished and with numerous, fine, concentric furrows or riblets. 



