﻿46 CHIILEROIDEI. 



P. 3069. Remains of distal two thirds of spine, showing part of the 

 posterior face. For some distance from the pointed 

 extremity this face is flattened or transversely concave, 

 but more proximally a faint median longitudinal ridge 

 begins to appear, bearing one or two denticles at wide 

 intervals. Ennishillen Coll. 



P. 3197, P. 3197 a, P. 4454 a. The distal half and two portions of 

 the distal half of small spines. The third specimen shows 

 some of the downwardly pointing posterior denticles, and 

 the non-tuberculated apical portion is very short. 



Ennislcillen Coll. 



P. 341. Distal half of small spine, showing denticles. 



Purchased, 1881. 



P. 427. Fragment of small spine, showing denticles. 



Par chased, 1882. 

 37376. Fragment of small spine, showing denticles. 



Purchased, 1863. 



41321. Fragment of large spine, showing denticles. 



Purchased, 1869. 



(ii.) Dentition. 

 P. 477. Type specimen of the so-called Ischyodus johnsoni, briefly 

 described, with an imperfect figure, by Agassiz, loc. cit. 

 The presymphysial tooth (" intermaxillaire," Agassiz) lies 

 between, the two mandibular teeth (" maxillaires supe- 

 rieurs," Agassiz), of which that of the right side is almost 

 destroyed. One of the palatine teeth (" maxillaire infe- 

 rieur gauche," Agassiz) is also exposed, from the oral 

 aspect, but its outline is partly obscured or broken away. 

 None of the teeth can be removed from the matrix, owing 

 to its hardness, and they are not arranged so as to permit 

 of the satisfactory drawing of the entire specimen ; the 

 characteristic left mandibular tooth is, however, shown 

 from the oral aspect in PL II. fig. 3. The symphysial 

 facette of this tooth is narrow, and in the middle of the 

 oral face there is a broad prominence, separated from the 

 symphysial and post-oral margins by deep depressions ; the 

 extended, tubulated, tritoral area seems to have been con- 

 tinuous over the oral face, though rapidly thinning towards 

 the outer margin and evidently originally covered with a 

 stratum of hard dentine upon the inner face. The pre- 

 symphysial tooth seems to have been bilaterally symme- 

 trical, the tritoral portion forming a thick layer upon the 



