84 Dr. H. Riley on the Squaloraia. 



The animal is imbedded in the lias with its belly downwards ; whilst, there- 

 fore, we have an excellent view of the whole of its superior surface, we have 

 no means of observing its inferior or abdominal. It has, however, on the 

 most superficial inspection, a strong resemblance to the flat cartilaginous fishes; 

 and this is not confined to the form alone, for there are distributed all over its 

 surface an immense number of spines with radiated bases, (Plate IV. Fig. 

 1 — 3.) the remains of its dermoid apparatus. They are best seen around the 

 head, and on each side of the terminal pieces of the head. These spines are 

 identical with those of the Rays. 



In studying the head (Plate IV.) we can distinctly observe at its posterior 

 face or boundary, two processes projecting backwards, flattened laterally, and 

 bounding the occipital hole ; being evidently the remains of occipital con- 

 dyles. Allowing for the process of flattening, the forms of this region are 

 not unlike those of the Rays. 



Superiorly, and on the median line corresponding to the occiput, the bone 

 or cartilage has been greatly defaced ; but the parts between the orbits are in 

 excellent preservation. They are much depressed on the median line, but rise 

 in elevation as their lateral portions form the internal boundaries of the 

 orbits. 



This space in form and position, and indeed in all its characters, has a very 

 close resemblance to the same region in the Rays. In them the cartilage 

 corresponding to this space, becomes a mere membrane, and is termed the 

 " fontanelle." 



The depression and flattening in our specimen might have depended on 

 the same modification*. 



In front of the " fontanelle" are two terminal prolongations. The superior 

 has been fractured at its posterior extremity, and thrust backwards as far as 

 the anterior edge of the orbits. It has likewise been broken in two other 

 places near the middle. It is elongated, conical, flattened posteriorly and 

 superiorly, but becomes more rounded towards its anterior extremity. 

 Firmly attached to its superior surface, are many of the small spines 

 already noticed. In its displacement it has been moved obliquely back- 

 wards, so that we are unable to observe the superior surface of the inferior 

 prolongation. 



This prolongation is likewise elongated and conical; its length was pro- 

 bably greater than the preceding, for its anterior extremity is broken and 



* This appearance of the interorbital region, has led the majority of observers to consider the 

 animal in question a Saurian : we trust, however, the arguments we have advanced are sufficient 

 to show the contrary to be the case. 



