NATURAL SCIENCES OF PHILADELPHIA. 417 



Length from extremity of beak over umbo to ventral margin *35 ; antero- 

 posterior dimension *29 ; elevation of umbo above plane of valve *20. 



Locality. Grindstone quarries, Pt. aux Barques, with Rhynchonella cameri- 

 fera, &c. 



None of my specimens of this singular shell are perfect, even as casts ; and 

 I should be induced to refer them to Platyceras, Conrad, were it not that five 

 would thus be sinistral and six dextral, while at the same time the very eam- 

 panulate aperture seems to suggest rather Cardiomorpha or Isocardia. 



Cakdiopsis, Meek and Worthen. 



Cardiopsi3 crenistriata, n. sp. Shell of medium size, gibbous ; hinge line 

 straight, rather short, joining the posterior margin by a regular curve which 

 proceeds to the ventral side where a more abrupt curvature separates the pos- 

 terior from the anterior border. Beak prominent, incurved, projecting a little 

 above the hinge line. Surface marked by a set of irregular concentric wrin- 

 kles, and a set of fine, regular raised concentric striae, the whole decussated 

 by conspicuous, radiating, unequal, wrinkled ribs, which are fine and some- 

 what regular on the beak, becoming irregularly crenulated in the middle of 

 the valve, and irregularly flexuous near the pallial border. 



Greatest length from the beak to the ventral margin over the umbonal slope 

 96 (100) ; angle between this and the hinge margin 55 ; convexity of left 

 valve -33 (34). 



Locality. Section 27, Columbia, Jackson county. 



This fossil differs from Cardiomorpha radiata, de Kon., (An. Foss. 109, pi. 

 ii., 6), in being less inflated all around the pallial region, and in being more 

 produced posteriorly, as well as in the characters of the striation. It proba- 

 bly agrees in generic characters. Its closest analogue is Cardiopsis radiata, 

 Meek and Worthen, (Proc. Acad. Nat. Sci., Phil., Oct., 1860, and June, 

 1861), = Megambonia Lyoni, Hall, (13th Rep. Reg. N. Y., p. 110), from which 

 it seems to differ only in its striation. 



Cardiopsis jejuna, n. sp. Shell small, somewhat orbicular, nearly equila- 

 teral, with a prominent sharp beak slightly turned forward. Hinge line ob- 

 tusely angulated beneath the beak, extending on each side to a subalate ex- 

 pansion of the (right) valve, between which points the curvature of the pal- 

 lial margin decribes about three -fifths of a circle. Beak projecting above the 

 hinge ; umbo excavated on the anterior side ; umbonal ridge tumid on the 

 posterior side. Characters of hinge and external surface unknown ; surface 

 of cast with a few concentric furrows. 



Length '38 (100) ; height -41 (108) ; distance from posterior extremity to 

 line drawn over umbonal slope '23 (61) ; from anterior extremity to same line 

 20 (53) ; convexity of right valve '12 (32). 



Locality. Railroad cut, three miles north of Napoleon, Jackson county. 



Cardiopsis megambonata, n. sp. Shell very small, ovate, with an elevated, 

 little incurved, nearly central beak, gibbous umbo and regularly rounded 

 margins, of which the ventral is most abruptly so. Slopes from the umbo 

 convex in all directions to the very margin. Anterior and posterior cardinal 

 margins similar and equal. Surface of casts striately ribbed, most distinctly 

 so toward the ventral border, and in some cases marked by rather strong con- 

 centric wrinkles toward the pallial margin. 



Height from beak to ventral margin -25 (100) ; length from anterior to pos- 

 terior margin -23 (92) ; convexity of left (?) valve -11 (44). 



Locality. Grindstone quarries, Pt. aux Barques, with Rhynchonella cameri- 

 fera, &c. 



Nucula, Lamarck. 



Nucula Hobbakdi, n. sp. Shell rather large, ovate-triangular, ventricose ; 

 beaks three-fifths the shell-length behind the anterior (longer) extremity, 



1862.] 



