170 AMERICAN MARINE CONCHOLOGY. 



Genus CRYPTODON, Turton. 

 Brit. Bivalves, 121. 1822. 



1. C. GOULDII, Philippi. Fig. 430. 



(Lucina.) Zeit., Malak., 74. 1845. 

 Lucina flexuosa, Gould (not Montagu), Invert. Mass., edit. i. 71, f. 52. 



Shell minute, white, ovate-globose, nearly equilateral; beaks 

 prominent, inclined forwards, and having a rounded impression in 

 front of them; surface smooth, white; glossy within, with minute 

 radiating lines. 



Length 7.5, height 8 mill. 



New England. 



2. C. OBESUS, Yerrill. Fig. 431. 



Am. Journ. Science, 287, t. 7, f. 2. 1872. 



Shell white, irregularly and rather coarsely concentrically 

 striated, much swollen in the middle; transverse diameter nearly 

 equal to the length; height considerably exceeding the length; 

 beaks prolonged and turned strongly to the anterior side; lunular 

 area rather large and sunken, somewhat flat, in some cases sepa- 

 rated by a slight ridge into an inner and an outer portion ; anterior 

 border with a prominent rounded angle; ventral margin prolonged 

 and rounded in the middle ; posterior side with two strongly 

 developed flexures, separated by deep grooves; interior of shell 

 with radiating grooves, most conspicuous toward the ventral edge. 



Length 15, height 18 mill. 



British America. 



More nearly related to C.flexuosus of Europe than to C. Qouldii. 

 The latter is thinner and more delicate, more rounded, relatively 

 much longer and much smaller. 



Genus MYSIA, Leach. 

 Menke, Syn., edit. ii. 112. 1830. 



1. M. PUNCTATA, Say. 



(? Amphidesma.) Journ. Philad. Acad., ii. 308. 1822. 

 Orbicular, with numerous minute concentric wrinkles and very 

 numerous minute punctures; within, a small rim or projecting line 

 runs near the edge from the hinge to the basal'margin. White. 

 Length and height 7.5 mill. 



Southern Coast. 



