]10 JOURNAL OF THi^: NEW JERSEY 



tulate process for a cartilage. Animal with the mantle almost 

 closed, aperture and foot small ; siphons united, partly or wholly 

 retractile ; gills elongated, two on each side. 



1. Mya, L. 



Shell oblong, gaping widely at the ends, left valve with a large, 

 in-qjecting, flattened cartilage process ; pallial sinus large. 



Animal with a slender, straight foot; siphons long, united 

 to the tips, covered Avith epidermis, only partially retractile. 



1. Mya arenaria, L. (Figs. 9-11)'. Shell ovate, anterior end 

 wider and regularly rounded, posterior end also rounded; sur- 

 face roughly wrinkled at the lines of growth ; epidermis thin ; 

 cartilage internal, between a pit under the umbo of the right 

 valve and the large projecting process from the left. Chalky- 

 white; epidermis dirty-yellow. Common size. — L. 85 ; H. 45 ; 

 W. 25 ; U. slightly nearer anterior end. — Whole coast. Abun- 

 dant in sand and grav-el, between tides; — the Clam of New 

 England. 



2. Mya truncata, L. Similar to the last except in shape and 

 epidermis ; this shell being obliqueh^ or squarely truncated at 

 the posterior end which is widely gaping, and the epidermis is 

 thick, tongh and prolonged beyond the posterior end into a tube 

 two or three times as long as the shell. L. 70; H. 40; W. 30 ; 

 U. nearer the posterior end. — Cape Cod and north. Rare. 



Family 31. SAXICAVID/E. 



Shell equivalve, thick, gaping at both ends; hinge with a 

 single cardinal tooth ; ligament external, prominent, solid ; pal- 

 lial impression sinuous. Animnl elongated ; mantle lobes united, 

 with a small o])ening for the slender foot ; siphons large, entirely 

 united or very nearly so, and covered with a thick skin. — Living 

 in sand or mud. 



* External JiL'-anient on the longer end of shell /. Saxicava. 



^' External ligament on the shorter end 2. Cyrtodaria. 



1. Saxicava, Bel v. 



Shell, when young, symmetrical, with two minute teeth in 

 each valve ; when old, it is rough aiid toothless ; oblong, equi- 

 valve, gaping, with an external ligament; pallial impression a 

 series of elongated pits. 



1. Saxicava arctica, L. Shell irvee^nlarly oblong-oval, the right 



