FISHES HETEROLEPIDAE OPHIODON ELONGATUS. 49 



The largest specimen observed is about twelve inches in total length, the head forming nearly 

 the fourth of it. &quot;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 th 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 the 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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