414 HISTORY OF THE FISHES OF MASSACHUSETTS. 
the middle of the side of the fish, terminates beneath the centre of the dorsal fin, 
above the anus. 
The third ridge commences below and anterior to the pectoral fins, and, bounding 
the sides of the abdomen, is continued to the tail. Besides these three ridges on 
each side, a seventh ridge, commencing at the throat, passes through the centre of 
the abdomen to the vent. Just above the termination of the second ridge, or that 
upon the centre of the sides, another ridge commences, which passes backwards to 
the termination of the first ridge, or that upon the side of the back, then, curving 
upwards to the sides of the back, takes the place of the first ridge, and is con- 
tinued to the tail. Back of the vent the abdominal ridge disappears, so that the 
space between the vent and the termination of the first ridge is hexangular. Back 
of the dorsal fin, the ridge upon the centre of the sides having disappeared, the 
body is quadrangular. 
In front of the anus are nineteen transverse plates, and in front of the dorsal fin 
are fourteen of these plates; between the anus and the caudal fin are forty-two of 
these plates. The portion of the abdomen just back of the vent is much wider 
than the rest of the body, and presents the membranous flaps, which approach each 
other at the median line, thus forming pouches or a false belly in which are con- 
tained the ova of the female. 
The dorsal fin is situated at the commencement of the second third of the body, 
or at a distance back of the tip of the snout equal to one third the entire length. 
It is slightly rounded above, and is longer than the head; the height of its rays 
is equal to about one fifth the length of the head. 
The anus is situated directly beneath the middle of the dorsal fin. 
The pectorals are rather small, and are rounded when expanded. 
The anal fin is exceedingly delicate, scarcely discernible without the aid of a 
glass. 
The caudal fin is fan-shaped when expanded; the extremities of the rays project 
slightly beyond the connecting membrane. 
The fin rays are as follows: — D. 45. P. 14. A. 3. C. 12. 
Length, six to twelve inches. 
Remarks. This species is frequently taken in nets, in the waters of Boston Har- 
bor, by boys, while catching minnows for bait. Its motions are exceedingly rapid, 
resembling the gyrations of the Colubride. In one of the specimens described in 
my Report, numerous ova contained in its false pouches were hatched soon after 
it was taken, and when I received it, two days subsequent to its capture, it was 
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