106 JOURNAL OF THE NEW JERSEY 



* But slightly gaping ; shell quite thick 1. Macfra, 



* Very decidedly gaping ; shell quite thin and fragile 2. Labiosa. 



1. Mactra, L. 

 Shell elongated, slightly gaping at the ends. 

 Animal with a fringed mantle open to the siphons ; foot with 

 a bend like a knee. 



* Over 50 long 1- 



* Under 20 long 2, 



1. Mactra solidissima, Dillw. (Fig. 8.) Shell large, solid, sub- 

 ovate to subtriangular ; spoon shaped cavity for the cartilage 

 very large and broad; muscular and pallial impressions very 

 distinct ; pallial sinus quite shallow ; lateral teeth long, thin, and 

 striated. Epidermis dirty brown. L. 110 ; H. 75 ; W. 45 ; U. f 

 An. 115°. Shell sometimes much larger at the north. The 

 southern and small form is var, similis. Say. — Whole coast. 

 Common. This is the Beech, Giant or Dipper clam. 



2. Mactra lateralis, Say. Shell triangular to quadrilateral, the 

 umbo and the posterior point making the most distinct angles 

 of the outline ; cartilage pits small and deep ; muscular impres- 

 sions deep ; pallial Hne distinct, with a shallow sinus ; surface 

 with minute concentric wrinkles, otherwise smooth and shining. 

 White, covered with a thin, dirty brown epidermis ; inside clear, 

 glossy white. L. 15; H. 12; W. 10; U. J; An. 120°.— Massa- 

 chusetts and south. Common. 



2. Labiosa, Schm. 

 Shell oblong, widely gaping, reflected posteriorly, and with 

 a distinct gonial ridge ; internal cartilage and external ligament 

 somewhat united. 



1. Labiosa canaUculata, Say. Shell ovate-orbicular, very thin 

 and fragile, inflated ; anterior end rounded, posterior somewhat 

 pointed ; surface covered with regular, rounded, concentric ridges 

 and grooves, which show also on the inside ; decidedly gaping 

 behind ; cartilage in pits and connected with a subexternal liga- 

 ment. White. L. 65-75 ; H. 55 ; W. 36 ; U. f — New Jersey 

 and south. 



2. Labiosa lineata, Say. Shell oval, thin, with both ends gap- 

 ing, the posterior end widely so ; gonial ridge keel like ; surface 

 unequally and very slightly wrinkled. White. L. 72 ; H. 50 ; 

 W. 28 ; U. f . — New Jersey and south. 



