330 
ACTIXOPTERYGII. 
of the jaws, smaller on the palatine and on the splenial, where they 
are in single series anteriorly, minute and almost granular on the 
other inner hones ; preoperculnm nearly smooth and narrow ; oper¬ 
culum deep, much broader helow than above, and suboperculum of 
moderate size. Ossifications in the sheath of the notochord insigni¬ 
ficant or absent in the smaller species, consisting only of separate 
hypocentra and pleurocentra in the largest species ; ossified ribs 
slender, not reaching the ventral border of the abdomen. Fulcra 
biserial, well-developed on all the fins, those of the pectoral being 
especially elongated and sometimes in part fused together. Pectoral 
much exceeding the pelvic fins in size, but the latter well-developed ; 
dorsal and anal fins triangular in shape, the former arising opposite 
or immediately behind the pelvic fins ; caudal fin deeply forked. 
Scales delicate, smooth, feebly crimped or in part tuberculated, 
deeply overlapping, and none much deeper than broad ; a few series 
anteriorly quadrangular and possibly sometimes united with peg-and- 
socket, the others more or less cycloidal, and very few narrowed on 
the ventral aspect of the fish. Lateral line inconspicuous. 
The osteology of Caturus as exhibited partly in specimens from 
the French and German Lithographic Stone, but especially in those 
from the English Oxford Clay, is proved to be essentially similar 
to that of Eugnathus already described (p. 287). The state of pre¬ 
servation of the Oxfordian fossils in the Leeds Collection, however, 
permits the determination of a few additional features. In advance 
of the basipterygoid process of the parasphenoid there is a very 
large alisphenoidal ossification, much exceeding in size either of the 
otics behind. The prootic is equally well ossified, and the opisthotic 
is still more robust; but no undoubted traces of pterotic and epiotic 
ossifications have hitherto been observed. As in Eugnathus , the 
mesethmoid appears to have been little ossified, and it was probably 
small. In front of the parasphenoid there is a pair of large vomers, 
bearing a few teeth only at their anterior end. The nasals are 
proved to resemble those of Araia. The^upraorbita'is are irregular 
and much subdivided at their outer margin, the tesserae extending 
somewhat upon the cheek. The symplectic in Caturus still remains 
unknown; but the palatine has been well observed in this genus, 
forming a small laterally compressed plate of bone with a row of 
teeth on its oral margin. The ceratohyal does not exhibit so much 
evidence of twisting as in Eugnathus. The gill-filaments have 
calcified supports, and there are small tooth-like gill-rakers, some 
arranged on the edge of little triangular flakes of bone like those 
observed in Amia. 
