10 
ACTINOPTERYGII. 
teeth ; mandible very deep posteriorly; a single opercular bone 
on each side. Head and opercular bones ornamented chiefly with 
striations, sometimes reticulated and in part tuberculated. Long, 
slender ribs present. Fin-rays distantly articulated; fulcra absent. 
Paired fins small; dorsal and anal fins large, directly opposed; 
caudal fin truncated behind, symmetrical. Trunk with four longi¬ 
tudinal series of dermal scutes, one dorsal and another ventral, and 
a pair supporting the “ lateral line ” ; no intermediate scales. 
The cranium in this genus is completely enveloped in membrane- 
bones, which are more or less fused together in the adult and firmly 
connected at the side in advance of the orbit with the similarly 
fused cheek-plates. The constitution of the cranial shield is not 
satisfactorily known, but it extends backwards beyond the skull 
to the hinder border of the operculum. The parasphenoid, as seen 
in side view, appears curved, the convexity being downwards ; a 
short and broad plate extends from it on each side over the otic 
region : and the bone is also prolonged backwards beyond the skull 
to the same degree as the cranial roof already noted. The orbit 
is large, and there is distinct evidence of an ossified sclerotic, or at 
least of a hardened sclerotic ring. The nasal opening is single on 
each side, and obliquely elongated; and whatever appearance there 
may be of a second smaller opening between the latter and the 
orbit in certain specimens, must be regarded as deceptive. One 
long posterior suborbital bone is distinct, deepest behind, and pro¬ 
duced as a narrow bar beneath the orbit; but nothing further is 
definitely known concerning the limits of the premaxillae, maxillae, 
and the other elements of the cheek. The hyomandibular is not 
much expanded at either extremity, and its long axis is nearly 
vertical; the quadrate is relatively large and triangular in shape. 
The mandible is deepest at its hinder extremity, and its posterior 
border descends almost vertically from the articulation with the 
skull. The angular and articular bones are fused together, and 
the expanded outer surface of the former is marked by radiating 
branches from the sensory canal which traverses its length. As 
to the limits of the dentary and splenial, there is no precise in¬ 
formation ; but the fact that a double series of large teeth extends 
quite to the termination of the mandible, suggests that there is 
no presymphysial bone. The dentition on the margin of both jaws 
consists of a series of large, enamel-tipped, conical teeth, well 
spaced, with minute intermediate teeth ; and some of the inner 
bones of the mouth are also provided with minute teeth. A small 
oval operculum is attached by an articulation near the upper end of 
its anterior border to the hyomandibular; but there is no evidence 
