CHIMiERIDiE. 
53 
The genera and species of this family are distinguished by the 
characters of the dentition ; and in the case of most of the extinct 
forms this is the only part of the skeleton available for study. A 
convenient nomenclature for the various parts of the teeth has thus 
been proposed by E. T. Newton 1 ; and this will be adopted in the 
following pages, except that here the term “ tritor ” is substituted 
for “ tooth.” 
Synopsis of Genera. 
A. Outer tritors of mandibular teeth two (an¬ 
terior and posterior). 
Mandibular tooth with narrow symphysial 
surface, and external thickening along 
the oral border. Palatine tooth with 
deeply cleft posterior border, and the 
tritors in an outer and an inner lon¬ 
gitudinal series . Ganodus (p. 55). 
Mandibular tooth with narrow symphysial 
surface, and external thickening along 
the oral border. Palatine tooth with 
four tritors, two being inner, one 
median, and one outer; no posterior 
excavation ... Ischyodus (p. 59). 
Mandibular tooth with broad symphysia 
surface, and no external thickening 
along the oral border. Palatine tooth 
with three tritors, two being inner and 
one outer; no posterior excavation . . Edapliodon (p. 73). 
B. Outer tritors of mandibular teeth absent. 
Mandibular tooth with narrow symphysial 
surface, and external thickening along 
the oral border. Palatine tooth with 
single large tritor divided into two 
processes anteriorly. Callorhynchus (p. 87). 
0. Mandibular teeth thin, with the outer tritors 
small and numerous, and symphysis 
narrow. 
Mandibular tooth with two rows of dot-like 
beak-tritors and similar outer tritors; 
median tritor absent. [Palatine tooth 
unknown.] . Elasmodectes (p. 88). 
Mandibular tooth with large beak-tritor, 
this and the outer tritors being lami¬ 
nated ; median tritor present. Pala¬ 
tine tooth with four tritors, two being 
inner, one median, and one outer, the 
three first with tendency to fusion . . Elasmodus (p. 88). 
1 Chimaeroid Fishes, Brit. Cretaceous Bocks (Mem. Geol. Surv, 1878), p. 4. 
