IXOCERAMUS. 





spiral ; witli a very lar^'c iiiubo near the anterior end, ciirveil iiiwai-ils ami 

 forwards. Surface nearly sinootli, except for the presence of n'rowth-lines. 



Tlie liinge (Fig. 94) curves at either end ; it is thinnest near the umln) and 

 becomes thicker towards the posterior end. The ligament-pits are deep, almost 

 square, but sometimes oblong, and increase in height from the umbo posteriorly. 



1^. 



% 



/ 



I 



Fio. 92.— Ki^ht viilve and part of left valve of specimen shown in Figs. 90, 91. 



AfUnUies. — I. inrolufns i& the type of the genus or sub-genus Volcicem))nis of 

 Stoliczka. In general appearance this differs considerably from other species of 

 Inoceramus, so that its separation as a distinct genus or sub-genus seems at first 

 sight (juite justifiable ; but the study of a large number of specimens of /. iiiroliitiis 

 and I. Lamarcki shows that these two species arc very closely allied, and that the 

 former has almost certainly descended from the latter. Such being the case it 

 follows that these two species are more nearly related to one another than aiv 



