S IIUI.KIC, FOSSIL VEKTEBHATE REMAINS FROM SIM TZHERCi EN. 



fossil, these bones appear to diverge leaving an angle between 

 them into which the sharp auterior angle of a large, medianly 

 bisectcd rhomboid bone intrudes. No external nostril is now 

 discoverable. Whether or not it was at the end of the snout 

 caunot now, in the absence of this, be positively decided by 

 facts, but its position here is less probable in the absence of 

 any trace in the palate, or on the iipper surface of the snout 

 near its front, of a premaxillary-maxillary suture, which 

 with a terminal or subterminal external nostril might be 

 expected here. 



I am therefore inclined to think that the external nostril 

 was situated behind the two toothbearing boncs, to regard 

 these as the premaxilla^, and to interpret as nasals the pair 

 of bones forming the rhomboid plate which posteriorly intrudes, 

 between them and the upper surface of the snout. If these 

 conjectures prove correct (the imperfect condition of the fossil 

 will not allow me to form a positive opinion), the construetion 

 of the snout answers to the Ichthyosarian pattcrn. 



The teeth however have characters some which I have not 

 before met with in this genus. Portions of nine reijiain in each 

 premaxilla, and about as many more are represented by vacant 

 spaces. Eighteen teeth occupied a space of about five inches. 

 The front are rauch smaller than the hinder ones, and their 

 attachment to the jaw differs also from that of these. They stånd 

 in an open continous groove resting against its outer wall; 

 while the hinder teeth occupy separate sockets, the dentary 

 <i-roove being here interrupted by transverse partitions. These 

 are very distinct in a small separate fragment of the hinder 

 part of a jaw probably of another individual. No complete 

 crown remains, so that its form is not ascertainable from this 

 fossil. Seven of the teeth including all the small front ones 

 have been smoothly truncated through the neck as if by a 

 lapidary. All show a transverse section of a simple oblong 

 shape, the antero-posterior diameter being to the transverse 

 one as 2:1, or in some of them 2,5: i. Of three of the large 

 hinder teeth nearly 0,i inch remains projecting above the 

 outer parapet of the jaw bone, and it is marked with a rela- 

 tively coarse longitudinal fluting. If my conjecture of the 

 nature of this fossil prove correct, the lateral compression of 

 the teeth is much greater than in any other species known 

 to me, being much in excess of that obtaining in I. campylodon 



