LAMELLIBEANCHIATA OF .THE LOWER MARLS. 185 



but is less contracted in front, giving a wider anterior end, which makes it 

 appear proportionally longer. As compared with shells of L. elUpticmn, from 

 Tippah County, Mississippi, this one has been more slender in proportion 

 to its length, with extremities less broadly rounded, and the shell not so 

 high posteriorly. Mr. Gabb considers all these forms as only stages of 

 growth of L. planulatum, to which I do not agree. 



Formation and locality. — In the Lower Green Marls at Freehold, and 

 from the marl pits of G. C. Schanck, Monmouth County, New Jersey. 



Legutnen appressum. 

 Plate XXV, Figs. 6-8. 



Legumen appressa Conrad. J. A. N. Sci., new ser., Vol. Ill, p. 325. Gabb, Synop.sis, p. 



133. Meek, Check-list, p. 15. Geol. Surv. N. J., 1868, p. 727. 

 See Legumen appressa Conrad. Kerr's Geol. Eept. N. C, appendix, p. IG, citing J. A. 



N. Sci., Vol. Ill, p. 325, PI. XXXIV, Fig. 19, as this species; also the same 



figure given as L. ellipticiis, J. A. N. S., loc. cit. 



Shell transversely elliptical, about twice and a half as long as high, 

 with depressed convex valves and small, appressed beaks, which are situated 

 just within the anterior third of the length of the valves. Thickness of the 

 shell through the valves, in an uncompressed specimen, equal to two-fifths of 

 the height from the dorsal to the ventral margin. Anterior end of the shell 

 narrowed in front of the beaks and narrowly rounded at the extremity; pos- 

 terior end also sharpl}^ rounded, the longest part being above the middle of 

 the height; dorsal and ventral margins parallel, but each moderately curved. 

 Ligament proportionally long, imbedded in a narrow, deep esoutcheonal 

 area; lunular depression very slight. Surface of the shell marked by fine, 

 regular, even, step-like concentric ridges, strongest on the posterior part of 

 the shell. 



It is somewhat difficult to point out distinctions between the species of 

 this genus where they are preserved as internal casts only, the markings of 

 the surface being only partially or not at all preserved, and the form of the 

 shell scarcely indicated in the parts where most distinct when the shell itself 

 is examined. So far as I can distinguish, the casts which I have figured 

 belong to the L. planulatum, and appear to differ from the shell here used in the 



