INVERTEBRATE PALEONTOLOGY. 55 



/. prozirmis, apparently agreeing very nearly with it. Consequently, his older 

 name is now cheerfully retained for it. Professor Tuomey's description is so 

 brief and unsatisfactory, that I should not have ventured to refer our shell to 

 his species without the aid derived from a comparison with specimens from 

 near the same locality. 



It is possible that the form represented by our figs. 2, a, b, of pi. 12, 

 may belong rather to this species than to I. Bambini, to which I have very 

 doubtfully referred it. 



Locality and position. — Great Bend of the Missouri, below Fort Pierre ; 

 from the lower part of the Fort Pierre group ; also, Columbus, Miss., and 

 Alabama. 



I ii ocora in ii s proximus?, var. subcircnlaris, M. 



Plate 12, figs. 2, a, b. 



Compare Inoceramus Bambini, Morton (1834), Synop. Org. Remaius, pi. 13, fig. 11 (not pi. 17, fig. 3); and 

 I. Cripsii, Mantell (broad varieties). 



I have been more perplexed in regard to the proper disposition of 

 this form than any other in the collection. It closely approaches some of 

 those I have referred to /. Cripsii, var. Bambini, as may be seen by com- 

 paring it with fig. 3 of the same plate. Yet it not only differs in its shorter, 

 more rounded, outline, but is constantly more compressed, as may be seen by 

 fig. 2, b. In this latter character, as well as in its less depressed form, it 

 much more nearly resembles /. proximus (fig. 7 of the same plate), to which 

 I have concluded to refer it provisionally as a variety. It will be seen, how- 

 ever, to have proportionally larger and rather more distant undulations, which 

 also present a somewhat different curve, though the specimens vary somewhat 

 in these characters. 



Again, it may, on the other hand, be the young of I. Vanuxemi (pi. 14j 

 fig. 2). The objection to this view is, that it came from a somewhat distant 

 locality, where no large specimens agreeing with that form have been found ; 

 while it seems not to be very uncommon, and the specimens are quite uniform 

 in their small size. In several respects, it also resembles one of the forms 

 included by Dr. Morton under the name Bambini, (see our cuts, figs. 3 and 

 4, page 50), though not the one I regard as the typical form of that shell, 

 (represented by our cuts 1 and 2.) It is, however, decidedly more com- 

 pressed than either of Dr. Morton's types. 



