CniROCENlRlDJE. 
117 
backwards ; a series of small teeth on the ectopterygoid, and 
another very small series within the conspicuous row of mandibular 
teeth, this extending a little backwards upon the elevated coronoid 
region. Opercular apparatus complete, with some slender branchios- 
tegal rays. 
Tomognathus mordax, Dixon. 
1850. Tomognathus mordax, F. Dixon, Geol. Sussex, p. 376, pi. xxxv. 
fig. 1. 
1850. Tomognathus leiodus, F. Dixon, ibid. p. 377, pi. xxx. fiw. 31. 
[Mandibular rami ; British Museum.] 
1888. Tomognathus morda.v, A. S. Woodward, 1’roc. Geol. Assoc., 
vol. x. p. 313. 
Type. Imperfect skull, with jaws. 
The type species, the head with opercular apparatus attaining a 
length of 0-07. Orbit occupying nearly half the total length of the 
head, the maxilla nearly three and a half times as long as its maxi- 
mum depth, and the mandibular ramus a little more than three 
times as long as its maximum depth. The robust premaxillse fusedi 
together, and each bearing four large teeth gradually decreasing in 
size from the middle line to the side : these teeth scarcely tumid at 
the base, nearly straight, enamelled and faintly fluted in their 
distal half. None of tho maxillary teeth more than half as large 
us the latter, very slender, and rapidly becoming small in the very 
close series behind ; about eight teeth in the ectopterygoid series as 
large as the anterior maxillary teeth. Outer mandibular teeth 
closely similar to those of the prcmaxilla, but those at the sym- 
physis a little more tumid at the base and incurved at the apex ; 
the foremost tooth relatively small, the next three the largest, then 
another small one as the first of a diminishing series of about six to 
eight teeth. Width of operculum nearly equalling one quarter the 
length of the skull ; suboperculum wider than deep ; both destitute 
of superficial ornament. 
Form, cj- Loc. Turonian : Kent, Sussex, and Surrey. 
P. 9237. Imperfect skull in counterpart halves of a block of chalk ; 
unknown locality in S.E. England. The otic region of 
the skull, the pterygo-quadrate arcade (with teeth on the 
ectopterygoid), and the right mandibular ramus are dis- 
played. History unknown. 
P. 4844. Imperfect skull exhibiting part of the median occipital 
crest, the right postfrontal, the hollowed frontal region, 
the premaxillae, right maxilla, and the mandible ; S.E. 
England. Furclmsed, 1885. 
