PISHES—EMBIOTOCOIDAE—HYSTEROCARPUS TRASKII. 
191 
This is the only species of the family, so far described, as inhabiting the fresh waters ; it is 
said to occur in the lagoons of the lower part of the Sacramento as well as further up the course 
of that river. It would appear very remarkable if that family was excluded from the San Jao- 
quin and other rivers of California and Oregon, and the more so, that the marine representa¬ 
tives of this group occur all along the coast from San Diego to Puget’s Sound. 
The general form of the body, which is very much compressed, is sub-elliptical in its profile, 
the nape being convex, the dorsal and abdominal outlines regularly arcbed, whilst the frontal 
line is depressed immediately above the eye. The greatest depth of the body, corresponding 
pretty nearly to the middle of its length, is about the third, a little more or less, of the total 
length. From the origin of the anal the body tapers rather rapidly towards the peduncle of 
the tail, which is short. 
In the adult and pregnant female the outline of the body is very much disfigured; the inferior 
region, between the origin of the anal fin and the throat, is swollen and convex ; the head is turned 
upwards, rendering its upper surface sub-concave, giving to the mouth a very oblique direction, 
and to the lower jaw a projecting aspect. 
The head is rather small, constituting the fourth of the total length; it is a little longer than 
deep where deepest. The eye is circular and well developed, approximating the upper surface 
of the head ; its horizontal diameter being contained about three times and a half in the length 
of the side of the head, and nearly once in advance of the anterior rim of the orbit. The nos¬ 
trils are conspicuous, nearer the orbit than the tip of the upper jaw, and situated towards the 
upper surface of the snout. The latter is rounded and sub-conical; the mouth being small, 
slightly oblique upwards, with the upper jaw protruding somewhat beyond the lower. The lips, 
though conspicuous, are rather thin ; the inferior one being free all round. The posterior 
extremity of the maxillar bone extends to a vertical line drawn in advance of the anterior rim 
of the orbit. The teeth are short and sub-conical, inconspicuous, disposed upon one single row. 
The branchiostegals are slender and short, five on either side. The opercle is vertically elon¬ 
gated, and rather narrow horizontally ; the sub-opercle is a thin and narrow piece, quite oblique 
in its situation. The interopercle is well developed. 
The origin of the dorsal fin takes place opposite the upper edge of the insertion of the 
pectorals. It is composed of sixteen or eighteen spinous rays and ten or eleven articulated 
ones, the latter occupying about the two-sevenths of the base of that fin. The anterior 
spinous ray is quite small; the next ones increase in height to the fifth, sixth, and seventh, 
which are the highest, and higher also than the articulated rays, whilst the remaining ones 
diminish gradually backwards towards the articulated rays, which rise suddenly above the last 
spine. The articulated rays themselves are nearly equal amongst themselves, bifurcating but 
once upon their extend. The origin of the anal is situated opposite the eleventh or twelfth 
spinous rays. The anterior spine is generally a little larger than the third, but the second is 
always the longest of the three. The soft portion is composed of ten undivided rays, followed 
by eleven or twelve bifurcated ones. The rays of the caudal dichotomise three times ; the fin 
itself is furcated, and contained about six times in the total length. The origin of the ventrals 
takes place under the highest dorsal spine ; their tips or extremities reach, and even overlap, 
the vent to the anterior margin of the anal. The articulated rays sub-divide three times. As 
to the pectorals, they are of moderate development, for, their extremities do not extend as far 
