DERCETID^. 
171 
and there are no traces of transverse processes. The 
neural spines, ribs, and intermuscular bones are shown as 
in the previous specimen, and the characteristic dorsal 
fin-supports occur, without any traces of the fin itself. 
E-emains of the clavicle and supraclavicle occur; and the 
longest rays of the pectoral fins are about half as long 
as the head with opercular apparatus. No scales can be 
distinguished. Lewis Coll. 
49522. See p. 182. 
Family DERCETID^„ 
Head and trunk much elongated. Parietal bones of moderate 
size and meeting in the middle line ; squamosal suturally united 
with parietals and completely covering the otic region •; snout con¬ 
siderably produced ; cheek-plates delicate or wanting. Mandibular 
suspensorium vertical or inclined backwards, and gape of mouth 
very wide ; premaxilla delicate, extending in front of the ethmoidal 
region, and apparently forming the greater part of the upper border 
of the mouth; teeth conical and slender, in a single series on the 
margin of the jaws, clustered on the pterygoid arcade and the inner 
side of the mandible. Opercular apparatus complete, with few 
slender branchiostegal rays, but no gular plate. Vertebral centra 
in the form of delicate constricted cylinders pierced by the noto¬ 
chord ; ribs long and slender, borne by laminar transverse processes ; 
neural and haemal spines in the caudal region very short. Inter¬ 
muscular bones present. Fin-fulcra absent; fin-rays bifurcated 
slightly and articulated at wide intervals in the distal half; post¬ 
temporal bones in contact with the supraoccipital, and pectoral fins 
low down upon the flanks; pelvic fins well-developed, abdominal; 
a single dorsal fin, more or less extended; anal fin short; caudal 
fin separate. Ordinary scales small or wanting, but two or more 
continuous paired series of enlarged scutes along the flanks ; no 
median dorsal or ventral scutes. 
Synopsis of Genera. 
I. No scales between scutes. 
Dorsal fin occupying the greater part 
of the back, and anal fin opposed 
to its hinder portion ; scutes much 
expanded. Dercetis (p. 172). 
Dorsal fin not occupying more than 
one third of the back, and anal 
fin behind it; scutes not much 
expanded. Leptotrachelus (p. 173). 
