LAMELLIBRANCHIATA OF THE LOWER MAELS. 161 



C. spissa, and there is considerable difference between them even then; but 

 it is imjjossible in the absence of his type specimen to say how imperfect it 

 may have been or how near the figure may represent it. In this latter 

 respect, however, it is only fair to say that in general features his figures 

 are very expressive. The cast which I have figured and referred to the 

 species is oblately circular in outline, a little wider than high, with a small 

 apex, rather prominently convex disk, and wntli a posterior constricting 

 furrow in the line of the advancement of the muscular scar which is less 

 distinctly marked than on his figure, and the pallial line is also not so 

 marked. The posterior scar is distinct, of a large size, wliile the anterior is 

 scarcely visible. The shell lacks the angular anterior end, and is much 

 wider posteriorly than Mr. Conrad's figure. Still, I am strongly inclined 

 to believe it belongs to the same species. They both present much the 

 appearance of specimens of Lueina rather than Cyprimeria, but the one here 

 described may readily be imagined to have been twisted in an antero-pos- 

 terior direction. 



Formation and locality. — Mr. Conrad's specimen was from Ci'osswn'cks, 

 New Jersey, while the one here used is from the Lower Marls at Holmdel, 

 Monmouth County, New Jersey, and is from the collections of the Rev. Dr. 

 Eiley. 



Genus DOSIFIA Scopoli. 



Dosiuia Gabbi, n. sp. 

 Plate XXII, Figs. 4 and 5. 



Shell of medium size, not exceeding one and one-eighth inches in its 

 greatest diameter, subcircular in outline and moderately gibbous, with pro- 

 jecting beaks, which are directed forward and slightl}^ incurved. On the 

 internal cast there are evidences of two cardinal teeth in each valve, but 

 none of any laterals. The muscular imprints are large and but faintly 

 marked, and the pallial line is deeply sinuate ; the sinus deep and angular 

 and directed upward and forward. The cardinal margin is deeply inflected 

 as if for a wide hinge plate or ligament, and tlie edges of the depression 

 sharply angular. The surface of the cast bears evidence of strong concen- 

 tric undulations on the outer half of the shell. Some imperfect valves pre- 

 4418 MON 9 11 



