164 AMERICAN MARINE CONCHOLOGY. 



anterior margin concave, with a deep, broad lunule ; surface with 

 rather close concentric ribs and striae, thirty to forty in number, 

 sometimes obsolete towards the base ; inner margin simple. 



New England, northwards. 



4. A. DEPRESSA, Brown. Figs. 412, 415. 



(Crassina.) Brit. Conch. 96, t. 38, f. 2. 1827. 

 Astarte Warhami, Hancock. 



Astarte crebricostata, Forbes, Ann. Nat. Hist. , xix. 98, t. 9, f. 4. 1837. 

 Astarte lens, Stimpson, Yerrill, Am. Journ. Science, 287. Mar. 1872. 

 Astarte elliptica, Brown, Brit. Conch. 96, t. 38, f. 3. 1844. 



Shell large, moderately convex or depressed, beaks rather ob- 

 tuse, ovate-triangular ; anterior slope slightly concave, the poste- 

 rior end obtusely rounded or truncated ; with thirty to forty 

 squared concentric ribs, more or less obsolete towards the posterior 

 end or base. Margin finely crenate within. 



Length 27, height 25 mill. 



Maine, northwards. (Europe.) 



Dr. Gould writes of this species, " A series of the young may 

 be selected which would satisfy any one as to specific value ; 

 while intermediate specimens would so connect it with sulcata, 

 elliptica, Banksii, and compressor, as to be a complete puzzle. A 

 large compressed form, to which I notice that Dr. Stimpson has 

 attached a label in his collection with the name A. lens, I think 

 would fall under this species, though it merges almost as well into 

 A. sulcata." Mr. Yerrill distinguishes the American species from 

 depressa (crebricostata), under the name of lens ; I am inclined to 

 adopt a more conservative view, in this genus, where the specific 

 characters appear to be so greatly modified in different individuals. 



Figures 413-415 represent A. elliptica, Brown, which can 

 scarcely be designated as a variety. 



5. A. QUADRANS, Gould. Fig. 416, 417. 



Invert. Mass., edit. i. 81, f. 48. 1841. 

 Astarte Portlandica, Mighels, Proc. Bost. Soc. Nat. Hist., 129. 1843. 



Shell obliquety oval, anterior portion the longest ; , surface 

 smooth, very slightly wrinkled by growth-lines ; epidermis light 

 yellowish-olive ; hinge margin narrow, with a small lateral tooth 

 in the left valve, and a corresponding groove in the right valve ; 

 inner margin plain. 



Length 12, height 10 mill. 



Massachusetts, northward. 



