1h86,] fqualoraja polyspondyla. 537 



Affinities and Systematic Position. 



Proceeding, lastly, to a consideration of the systematic position of 

 Squaloraja, it will be observed that the new fossils here described 

 enable us to arrive at a much more definite conclusion than it has 

 hitherto been possible to formulate. Agassiz has pointed out the 

 affinities of the genus with the Pristiophoridpe ; Davies has further 

 indicated some resemblances to the Ehinobatidse, and been led, by 

 his discovery of the rostral spine, to speculate at least as to its 

 family distinctness ; while Giiuther' has likewise refrained from 

 more than a suggestion that it is nearly allied to the first-named 

 group. 



That the animal is a true Selachian, there cannot be the slightest 

 doubt ; nor does it require more than a superficial glance to recognize 

 its resemblance both to the Sharks proper and the Rays. But (as 

 already mentioned by Davies) the possession of a prehensile rostral 

 spine by the male distinguishes Squaloraja from all known members 

 of the order, recent or fossil, and suggests affinities with the Chi- 

 macroids ^ ; while the enormous size of the barbels or cirri seems to 

 have no parallel, at least among Hving forms. The dentition, too, 

 is evidently unique, so far as our present knowledge . extends, and 

 the marked character of the symphysis is a feature of peculiar 

 interest. 



Comparing the genus in other points with the various recognized 

 families upon the "borderland" of the two sections of the Selachii, 

 reference may first be made to the Rhinidae. 



Though agreeing with this group in the very shght depression of 

 the body, it is readily distinguished by the elongation of the snout 

 and the inferior position of the mouth ; and the anterior border of 

 the pectoral fin is much less produced forwards, owing to the relatively 

 smaller size of the propterygium. 



To the oft-mentioned Pristiophoridse, Squaloraja bears a remark- 

 able resemblance, both in the structure of the snout and the general 

 form of the body ; but there are no traces of teeth on either 

 boundary of the rostrum ; and if the peculiar dental armature of 

 the jaw may be quoted as a family character, this, too, will exclude 

 the genus from the present group. 



From the family of Pristidse, the Liassic form is still further 

 separated by the characters of the head and its anterior prolongation, 

 though agreeing tolerably well in the shape of the trunk and fins. 



There are also certain features that prevent its reference to the 

 Rhinobatidae. The structure of the pectoral fin in this family is quite 

 distinct from that of the fossil, the propterygial element being pro- 

 longed far towards the head, so that in some cases it is connected by 

 skin with the cephalic region. 



Its distinctness from other families is too obvious to require any 

 special mention, and Squaloraja is thus excluded from all recognized 

 divisions of the order, [t may even represent a hitherto unknown 



' A. Giiiuber, ' Sduly uf Fishes ' (18S0), p. .'{So. 



^ We regard tbe Chiinaroidei as a distinct orchr, i<jlln« ing I'rolebsor IIuxIcv, 

 Vvoc. Zool. !:Joc'. ]87(i, p. 57. 



