LAMELLIBEANCHIATA OF THE LOWER MAELS. 77 



The anterior end is obliquely prolonged beyond the line of the beak, and 

 the remainder of the general outline, according to the concentric undula- 

 tions of the surface, has been nearly circular or obliquely ovate, the greatest 

 prolongation being in the line of the apex and of the postero-basal angle. 

 The surface of one specimen from Holmdel (figured) is marked by strong, 

 distant, rounded undulations parallel to the apparent lines of growth. The 

 surface of this cast is marked by radiating line's of pustules, much elon- 

 gated, forming interrupted lines or radii, exactly as is common to internal 

 easts of /. Sagensis and other forms of Inocerami from the impure lime- 

 stones of the Black Hills of Dakota. (No. 4 of the Missouri Section, M. and 

 H ) Another individual, much imperfect but retaining parts of both valves, 

 from Freehold, N. J., indicates a circular form, with less convex valves, the 

 left side being the most convex and having the beak much larger than on 

 the right valve, as well as projecting much farther above the hinge-line. 

 Tliis specimen has the surface undulations much smaller and also much 

 more numerous than the Holmdel specimen above referred to, there being 

 three at least in the same space occupied by two on that one. In an irou 

 nodule from Keyport, N. J., obtained from the brick clays of that place, 

 there are the remains of several large individuals, imperfect and variously 

 distorted, but still perfect enough to give their true form and characters 

 These have also been circular in general outline, with moderately convex 

 valves, but the undulations are remarkably large and prominent, round on 

 the surface and in the depressions (some of them half an inch in width), 

 and their surfaces have been marked by moderately strong concentric lines 

 of growth All these variations are precisely like those observed in col- 

 lections of the species from the typical western locality of /. Sagensis Owen, 

 and may be seen in any collection of twenty individuals made at random 

 from that region. The form from Freehold, N. J., with close undulations 

 and compressed valves, is most nearly allied to the form usually referred 

 to I. Vannxemi Toumey, and might well represent that species, while all the 

 others would be properly classed as I. Sagensis. 



The New Jersey forms of the genus have, I think, been pretty uni- 

 formly referred to I. Barabini Morton, and generally without the least 

 question as to tlie accuracy of the reference. None of Morton's specimens, 



