U. S. P. R. R. EXP. AND SURVEYS—ZOOLOGY—GENERAL REPORT. 
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having priority of publication. The only differences which we observe between M. productus 
and H. troiobridgii consist in the former having a larger head, and a more anterior situation of 
the ventral fins. The specimens, however, are not sufficiently well preserved to enable estab¬ 
lishing these differences with certainty, 
HOMALOPOMUS TROWBRIDGII, Grd. 
PjjATE XLa, Figs. 1-4. 
Spec. Char. —Snout pointed ; mouth deeply ©left; posterior extremity of maxillary extending to a vertical line drawn 
through the posterior rim of the pupil. Eye large. Second and third dorsals continuous ; anal fins continuous also. Extremity 
of pectorals reaching the anterior margin of the anal fin. Greyish brown above ; silvery grey beneath. 
Syn .—Hotnalopomus trowbridgii, Grd. in Proc. Acad. Nat. Sc. Philad. VIII, 1856, 132. 
The general aspect of the fish is elongated and very much tapering posteriorly. The length 
of the specimen figured is nineteen inches and a half. The head is sub-pyramidal, entering 
four times and a half in the total length. The lower jaw is longest, protruding beyond the 
upper, hence the gape of the mouth is directed slightly upwards. The posterior extremity of 
the maxillary extends to a vertical line drawn across the posterior rim of the pupil, that is, 
exactly midway between the tip of the lower jaw and the origin of the pectorals. The pre- 
maxillaries and dentaries are provided with a double row of canine teeth, largest upon the 
inner row. The teeth themselves are conical, acerated, and curved inwardly. The symphysis 
of the premaxillaries is toothless, so that a smooth area is observed at the anterior part of the 
upper jaw. Small, acerated, canine teeth exist upon the front of the vomer. The palatine 
hones are toothless. The tongue, broad, thick, fleshy, rounded upon its anterior thin margin, 
is perfectly smooth upon its surface. The eye is large, sub-circular, its horizontal diameter 
entering five times in the length of the side of the head. Its posterior rim is nearer the base 
of the pectoral fins than the extremity of the snout. The nostrils are situated a little in advance 
of the orbit. The gill openings are broadly cleft, and are continuous under the throat ; the 
brancliiostegal rays are seven in number on either side. The bones of the opercular apparatus 
are perfectly smooth, there being neither spines nor serrations upon their edges. The limb of 
the preopercle exhibits a series of very large mucous follicles, not unlike the cavernous bones of 
Sciaenoids. 
The body is compressed, lanceolated, thickest anteriorly, very much tapering posteriorly. 
The greatest depth enters about six times in the total length. The peduncle of the tail not 
occupied by the fins is very narrow ; its termination is spear-shaped, and surrounded by a 
slender caudal fin, concave upon its posterior margin. The anterior dorsal fin is comparatively 
small, sub-triangular in general appearance. A vertical line dropped from its origin passes 
immediately behind the' base of the pectorals. It is composed of ten slender articulated rays, 
the third of which is the longest; they bifurcate towards their tips. The second dorsal is 
continuous with the third, there being a depression in the outline to indicate the separation 
between the two fins. In the specimen now before us, from nineteen to twenty inches long, the 
second dorsal is separated from the first by a space of half an inch. It is the longest of the 
three, and also the lowest in the absolute The rays are articulated and bifurcated. The third 
dorsal is somewhat longer, and a little lower than the first, its rays being more highly bifurcated 
than in the two preceeding. The caudal is sub-crescentic upon its posterior margin, and 
