424 



J. W. DAVIS ON THE FISH-REMAINS OF 



sils &c. p. 626, pi. 3. i. figs. 21, 22, 23), from the limestone of 

 Armagh, bears a greater resemblance to this specimen than, perhaps, 

 any others ; but it may be easily distinguished by the greater 

 breadth of the crown of the tooth compared with its depth, the com- 

 paratively wide and short, somewhat cone-shaped character of the 

 denticles, and the tips of such denticles appearing minutely crenu- 

 lated under the lens. 



The specimens serving for the above descriptions were collected at 

 Aust by Mr. Ord, and are from his cabinet. In recognition of his 

 energetic and painstaking labours, I have ventured to employ his 

 name to distinguish this species of Gtenoptychius. 



Ctenopttchitjs pectinattts, Ag. 



A second species of Gtenoptychius has also been found at Aust, 

 and forms a part of the collection of Mr. Ord, of Bristol. It is -2 

 inch across the crown, and has a depth from the upper edge of 

 the crown to the base *15 inch. The crown is composed of 

 about 12 denticles, the tips of which extend almost in a straight 

 line ; at the apex the denticles terminate in short pointed cones. 

 Towards the body of the tooth these speedily coalesce and form 

 plications extending more than half the distance towards the base ; 

 they form a concave surface anteriorly, the base becoming thicker 

 and convex. The two outermost denticles, stronger than the re- 

 mainder, are continued in a semicircle, and converge towards the 

 base. The whole of the exposed surface is covered with a black, 

 shining enamel. 



In the third volume of the £ Poissons Fossiles ' *, M. Agassiz 

 describes and figures under the name of Ctenoptychius pectinatus, 

 some small teeth obtained from the Eurdie-House Limestone. The 

 specimens figured present very considerable variations in form, but are 

 each characterized by the denticles forming the crown of the tooth 

 being less distinctly separated towards the apex, and the points, 

 instead of extending vertically, as in C. apicalis, diverge or radiate 

 from the centre, somewhat in the form of a fan. The beautiful little 

 specimen from Aust agrees sufficiently well with this description to 

 warrant its inclusion in the same genus and species. Its more 

 rounded basal termination is the most striking point of divergence, 

 C. pectinatus having a more contracted stem-like or prolonged basal 

 portion. 



Cladodtjs ceetes, Davis. (Plate XXII. fig. 9.) 



This tooth offers some peculiarities which give it a distinctive 

 character. It is imbedded in the matrix ; and on the lower part it is 

 slightly imperfect. It consists of a wide and thick base, from the 

 centre of which springs a cone-shaped cusp. On either side the 

 central cone there are indications that at least one secondary cusp 

 has existed. The bony structure is very dense, and now of a deep 

 brown colour. The length of the base is -4 inch ; and the 

 height of the central cone is *3 inch. The latter is rather less 



* Page 100, tab. 19. figs. 2, 3, 4. 



