164 AMERICAN MARINE CONCHOLOGY. 
anterior margin concave, with a deep, broad lunule; surface with 
rather close concentric ribs and strize, 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. 1887. 
Astarte lens, Stimpson, Verrill, 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. (Hurope.) 
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 swlcata, 
elliptica, Banksii, and compressa, 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 wellinto 
A. sulcata.” Mr. Verrill distinguishes the American species from 
depressa (crebricostata), under the name of Jens; 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 varicty. 
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 obliquely 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. 
