534 MH. A. S. WOODWARD ON [DcC. 7, 



and for two thirds of its extent it is directed outwards and ex- 

 hibits only very slight tapering ; the distal thiid rapidly diminishes 

 to a pointed extremity and is fixed at right angles to the rest in a 

 backward direction. The hinder appendage (ci.b) measures only 

 two thirds the length of the first, and is about half as broad ; it 

 likewise has an outward and posterior trend, but (in its fossilized 

 state) is much more gradually arched. 



The relatively great size of these appendages renders them some- 

 what difficult of interpretation, and it is scarcely possible to decide 

 whether they consist of true cartilage or are merely dermal in cha- 

 racter. In position they correspond very closely with the hinder 

 labials of many living Selachians, and also with the supposed homo- 

 logous rods that form the axes of the oral barbels in Myxinoids^ 

 But in the latter group these appended " feelers " never seem to 

 extend outwards to a lengtli much exceeding half the breadth of the 

 head ; and the largest cirri with which I am acquainted in the Sel- 

 achians are scarcely longer than the rami of the jaws. It seems 

 likely, however, that the structures in Squaloraja are the gigantic 

 representatives of the latter, which are elongated outgrowths of the 

 cartilages of the nasal valves^. 



There is no evidence of anterior labials in the specimens of Squa- 

 loraja already known. 



Dentition. — The dentition of Squaloraja is very remarkable and 

 has not hitherto been correctly noted. Some indications are to be 

 observed in specimens I. and II., but the teeth are beautifully dis- 

 played both in III. and IV.; moreover, the parts in these two 

 instances are practically identical, showing that there were no vari- 

 ations according to sex, as is the case among certain living Selachians 

 (e.g. Raja). The dentition of both jaws is preserved in no. III. 

 (figs. 3, 4), but only that of the right side of the mandible affords a 

 good view of the grinding-surface. Each ramus bears only a single 

 dental plate, sharply marked off in front from its fellow of the oppo- 

 site side, and exhibiting towards the symphysis a gently tumid 

 prominence. For the anterior two thirds of its length the plate is 

 of nearly uniform breadth, but in the last third the outer border 

 gradually trends inwards, producing a more or less pointed posterior 

 extremity. And the efficiency of the grinding-surface is increased 

 by a series of parallel longitudinal ridges or folds of the enamel, which 

 are distinctly worn down towards the outer functional border. Eleven 

 of these rugi3e can be counted on no. III. (fig. 4), while fourteen or 

 fifteen are visible in no. IV ; but, except on the under surface of the 

 plate in no. II., there are no traces of any sutures between them, and 

 even in this specimen the evidence is somewhat obscure. It 

 appears, however, that there were feebly marked longitudinal divi- 

 sions corresponding to the several rugae, and that these became 

 accentuated at the outer edge, allowing of the shedding of the worn- 

 out portions as growth proceeded. 



' W. K. Parker, he. cif. pp. 38.5, 399, pis. x., xvii. figs. 1-3. 

 ^ The " Nasenfliigelknorpel " of Miiller ; see 0. Gegenbaur, ' Das Kopfskelet 

 der Selachier,' pp. 97-111, pLs. xvi., xvii. 



