Dr. H. Riley on the Squaloraia. 85 



has been lost. The superior surface instead of being convex like the former 

 has a very wide and superficial groove, the boundaries of which are the edges 

 on each side, elevated into a corresponding ridge. 



These ridges are higher and wider posteriorly than anteriorly. 



The form of these terminal cartilages in the llhinobatis is, in their essen- 

 tials, like that of our specimen. 



In studying the lateral regions of the head, and proceeding from behind 

 forwards, we find the parts posterior to the orbits much injured; portions, 

 however, of bone or cartilage may be seen on the posterior edge of the left 

 orbit, extending downwards and forwards, so as to constitute its lateral and 

 external boundary. From the position, form, and direction of these frag- 

 ments, supposing the fish to be a cartilaginous one, we think they are probably 

 the remains of the os quadratum. The orbits themselves are of large size, 

 and well defined, particularly the left. In front of the orbits is, on each side, 

 a large elliptical mass. In form and position it resembles those swellings of 

 the cartilage which in the Plagiostomes, and the Skates in particular, con- 

 stitute the seat of the organs of olfaction. These olfactive cavities are much 

 compressed vertically*. 



These spaces have on both sides a number of pieces or parts more or less 

 connected with them ; but having evidently undergone great mutilation, 

 their determination becomes a matter of some difficulty. We cannot trace 

 any connexion between them and the anterior extremities of the thoracic 

 members, which in many cartilaginous fishes are prolonged as far as this 

 point. Are they feelers? or, are they bones or cartilages extending from the 

 upper to the lower jaw .? 



* Since the above memoir was written, this country has been honoured by the presence of 

 Dr. Agassiz of Neuchatel, and gladly did we avail ourselves of the opportunity, during a transient 

 visit he made to the city of Bristol, of laying before him our very interesting fossil : we now with 

 much pleasure acknowledge that to his keen observation and perfect acquaintance with the science 

 of Ichthyology, we are indebted for some determinations which had escaped us. On removing 

 with his penknife some fragments of shale, he discovered several minute teeth along the line 

 separating the elliptical masses or olfactive cavities from each orbit : therefore these portions must 

 be considered as the olfactive cavities pressed closely against the maxillary bones ; and in the 

 line of their contact, and consequently along the anterior edge of the orbit, would be situated the 

 teeth attached to the superior maxillary bone having its usual position. A reference to these parts 

 in the common Skate will render this very evident. 



Tiie overlooking this circumstance in our determination of these parts, and the rectifying of our 

 error by Dr. Agassiz, lead us to withdraw the specific name of Dolicognathus as being no longer 

 applicable : we hope ere long to have the pleasure of seeing Professor Agassiz's views regarding 

 this very curious fish, registered in his Poissons Fossiles. 



