NATURAL SCIENCES OP PHILADELPHIA. 365 



character will separate it from C. Monmouthensis. The upper portion of the 

 posterior end, which, in the latter species, is distinctly angular, is broadly 

 rounded off in the present one. The beaks are also much more distant, nar- 

 rower and more acute, the two sides sloping up at about the same angle. The 

 muscular scars are of about the same shape, the posterior ones longest, while, 

 in C. Monmouthensis they are smallest. The anterior end is more prominent than 

 the corresponding portion of C. Delawarensis nob., the posterior end more pro- 

 duced, the truncation being of a similar character, but more oblique, and the 

 basal emargination very distinct, while in the latter form it is often entirely 

 absent. This species seems to be very rare, since this specimen is the only one 

 I have ever seen. 



Axin^a Poli. 



A. subaustralis Gabb. (Peclunculus Australia Morton). Dr. Morton says 

 in his synopsis, " I possess casts of another species from the marls of New Jer- 

 sey." 



These casts I have always considered as belonging to the above species, but 

 had no proof except that they corresponded in size and form to his type. I have 

 now before me undoubted proof of the correctness of my opinion in the shape 

 of three specimens, two of single valves, the other with both valves in contact. 

 I am indebted to the kindness of Dr. G. Brown, the courteous curator of the 

 collection of the Mt. Holly Society, for these specimens. 



Pecten Gault, Linn. 



P. Texanus Gabb, (Yirgatus Roem. not Nills.) This form is undoubtedly 

 distinct from the P. virgatus of Nillson and Goldfuss. It is a broader and 

 shorter shell, and with the ribs, over the surface, more than twice as numerous. 

 I have frequently observed casts in the New Jersey marls, and there is a piece 

 of shell from Alabama in the collection of the Academy which I cannot sepa- 

 rate from this species, as described and figured by Dr. Roemer. It may be that 

 they differ by the sides, from the beaks to the widest portion of the shell, being 

 longer and straighter. They show the same equivalve, compressed form, and 

 are twice as large as Dr. Roemer's figure. The ears I have never seen. 



P. Nillssonii Roem. does not correspond, certainly, with Dr. Goldfuss' 

 species; the markings are the same, but the form is somewhat different and 

 the ears are very distinct. The right ear of the right valve is very slightly 

 emarginate, (see figure.) He says, " Das rechte Ohr der rechten Klappe fur den 

 Bijssus deutlich ausgeschmtten," while in Goldfuss' figure pi. 99, fig. 8, b, it is 

 very deeply emarginate, the extremity being widened and the hinge line con- 

 cave. 



It may be P. Burlingtonensis nob., Jour. Acad. 2 Ser. Vol. 4, pi. 48, fig. 25, in 

 which the artist has represented a few slight undulations in such a way as to 

 convey an erroneous impression that they are almost concentric ribs. The sur- 

 face is plain or very obscurely undulated, and it is marked by fine concentric, 

 very slightly prominent imbrications. 



Neithea Drouet. 

 Pecten, Janira, pars Auct. 



N. M o r t o n i , nob., Janira id. d'Orb., Pecten quinquecoslata Mort. not Sow. 

 Dr. Morton says, "This fossil is beyond a doubt specifically identical with the 

 one described by Sowerby, and so characteristic of the cretaceous strata of 

 Europe ;" but as d'Orbigny justly observes, all the species of this group have 

 been confounded under one specific name. 



With the latter author, I believe it to be undoubtedly different from that 

 species. It is a very common fossil in some of the beds of the Jersey, and I 

 have observed it from Alabama and Tennessee. I have a very fine specimen 



1861.] 



