46 
CHIMiEROIDEI. 
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. Enniskillen 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. 
Enniskillen 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 pres 3 ’mphysial 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 PI. 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 
