FISHES-HETEROLEPIDAE-OPHIODON ELQNGATUS. 
49 
The largest specimen observed is about twelve inches in total length, the head forming nearly 
the fourth of it. The greatest depth of the body, taken across the middle of the abdominal 
region, enters about six times in the total length ; the greatest thickness is one-third less than 
the depth. Both, depth and thickness, taper posteriorly, giving the body a sub-fusiform profile 
and a compressed shape. The peduncle of the tail is slender and short. 
The head is sub-conical; its upper surface depressed and sloping forwards. The eye, situated 
towards the upper portion of the side of the head, is rather large and sub-elliptical in shape. 
Its horizontal diameter is contained five times in the length of the side of the head, once and a 
half in advance of the orbit. The nostrils are nearer to the orbit than to the tip of snout. 
The mouth is deeply cleft; the posterior extremity of the maxillary extending to a vertical line 
which would pass behind the orbit. The lower jaw is somewhat longer than the upper. The 
maxillaries are toothless ; canine teeth, slender and curved backwards, are observed on 
both of the jaws, on the vomer, and on the palatines. The largest may be observed distant 
along the dentaries (lower jaw), where they constitute a series, with smaller ones between. 
They are equally large at the inner and anterior extremity of the premaxillaries (upper jaw), but 
the rows which they constitute along the branch of these bones are rather slender. On the vomer 
they are of various sizes, and intermingled, constituting a patch convex forwards. A narrow 
and elongated band exists along the palatines, small and exiguous, somewhat similar to those 
occupying the extreme external margin of the upper jaw. The tongue is smooth, thin, 
cochleiform. The bony arcade across the cheeks is narrow, but more conspicuous than in 
Chiropsis. The cheeks and upper part of the opercle exhibit streaks of minute scales. The 
limb of the preopercle is provided with small spinous processes, the uppermost directed 
backwards, the lowermost forwards. The opercle is sub-triangular, terminating into a point 
posteriorly. The subopercle is very long, well developed, extending a thin blade beyond the 
opercle. The branchiostegal rays, six on either side, are well developed ; the branchial 
apertures are continuous under the throat. 
There is a long and continuous dorsal fin, extending from a line intersecting the posterior 
curve of the preopercle to a short distance from the base of the caudal. It is composed 
anteriorly of slender spinous rays, occupying the five-eighths of the entire base ; the spines are 
mostly tbe deepest anteriorly, diminishing gradually posteriorly ; and since the fins extend over 
that portion of the body which is declivous forwards, this circumstance gives to the upper edge 
of this portion of the fin a sub-convex outline. The soft or articulated portion is deepest in the 
middle with a sub-convex outline sloping anteriorly just as the spinous portion is sloping 
posteriorly, the two lines meeting at the junction of the two portions of the fin where the 
outline is most depressed. A space of about an inch and a quarter separates the posterior rays 
of the dorsal from the base of the central rays of the caudal. The latter fin is of moderate 
development, slightly emarginated posteriorly ; it is contained about eleven times in the total 
length.. Its middle rays bifurcate three times upon their length. The anal, convex exteriorly, 
is somewhat deeper than the dorsal, and a little longer than the soft portion of the latter. 
Posteriorly they are nearly even. The rays are all soft or articulated, the three anterior short 
and slender, bifurcating only once towards their extremity. The insertion of the ventrals is 
situated behind the base of the pectorals ; there are five, twice bifurcated rays, and an external 
slender spine closely united to the next articulated ray. The rays of the pectorals bifurcate but 
once ; the nine uppermost are more slender than the eight remaining ones. The posterior 
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