448 
ACTIN OPTEET GII . 
smaller than the trapezoidal operculum, from which it is divided 
by an oblique suture ; branchiostegal rays numerous. Pleurocentra 
and hypocentra in notochordal sheath fused or separate. Fin-fulcra 
small, extending along the foremost ray of each of the fins. Pectoral 
not excessively large, but much exceeding the pelvic fins in size; 
dorsal and anal fins triangular in shape, not extended, the former 
t opposite or arising somewhat behind the pelvic fins; caudal fin 
deeply forked. Scales thin, deeply overlapping, usually with an 
inner rib and peg-and-socket articulation, and the external layer of 
ganoine smooth or feebly ornamented; principal flank-scales deeper 
than broad, ventral scales in part broader than deep ; no enlarged 
series of ridge-scales, but a large scale at the base of one or both 
lobes of the caudal fin, and three slightly enlarged scales round the 
anus at the base of the anal fin. Lateral line opening by widely 
separated large pores. 
Little can be added to the osteological characters of this fish 
noted in the generic diagnosis. In the axial skeleton of the trunk 
the pleurocentra and hypocentra are delicate, always directly 
Head, etc., of Pholidophorus mcicrocephalus, left lateral aspect (after Zittei). 
cl., clavicle ; fr., frontal; i.op., interoperculum; rad., mandible ; rax., maxilla ; 
na., nasal; op., operculum ; pa., parietal ; pmx., premaxilla; pop., pre¬ 
operculum ; psph., parasphenoid ; pt., supratemporal; scl., “ supraclavicle ” 
(? post-temporal); so., suborbital; sop., suboperculum. 
opposed, not alternating ; but it is difficult to determine whether or 
not they usually fuse into complete rings. In the abdominal region, 
the two halves of each neural arch appear to be separate from each 
other and from the spine they support; while the ribs are delicate 
and extend only about half-way to the ventral border. The remote 
situation of the anus is indicated not merely by the enlarged median 
and paired scales surrounding it, but also by coprolitic matter in 
