LAMELLIBRANCHIATA OF THE LOWEE MAELS. 79 



Inoceramus Sagensis, var. quadrans. 

 Plate XIV, Fig. 16. 



Among the collections of the Academy of Natural Sciences, Philadel- 

 phia, from near BurHngton, N. J., there is a large cast of an Inoceramus pos- 

 sessing many of the features of /. Sagensis Owen, but differing in the form, 

 being quadrangular instead of circular, or very broadly ovate like that one. 

 This quadrangular feature is so marked, and so distinctly one pertaining to 

 the habit of the shell, that it seems like doing violence to one's ideas of 

 specific distinction to class it under the head of any described form. In 

 size and in the strength and distance of the undulations of the surface, as 

 well as in its general convexity, it corresponds very well to most specimens ot 

 /. Sagensis^ but the direction of the undulations indicate that the cardinal 

 and basal margins have been subparallel, or gently diverging backward or 

 to the umbonal ridge. The anterior' end is almost squarely truncate, a 

 little longer at the hinge than below, and the whole anterior slope from the 

 beak to the margin of the valve is very abrupt and strongly ridged; the 

 posterior end is prolonged and rounded below the middle of the shell, and 

 obliquely truncate above to the extremity of the hinge, giving to the whole 

 outline a somewhat rhombic character. The beak is very large and prom- 

 inent, somewhat more so than is common in I. Sagensis^ and very ventri- 

 cose, while the whole valve is marked by strong, distant, although irregular, 

 undulations, which become less marked and often duplicate on the posterior 

 cardinal slope. The middle of the cast for about two-thirds the width 

 is marked by strong, rather deep pits, connected by shallow furrows, 

 show^ing that the interior of the shell was covered by strong pearl-like pro- 

 tuberances, which progressed with the growth of the shell as does a muscu- 

 lar scar, and I presume they were connected in some Tvay with the vascular 

 system as were the lines of dots or interrupted stride on other species of the 

 genus This is the only specimen which I have seen from either New Jersey 

 or elsewhere possessing the peculiar quadrangular outline, but I presume 

 if the locality were more thoroughly examined or carefully watched others 

 would be obtained. 



