FISHES OF PENNSYLVANIA. 99 
the length of the head and about one-fourth of the total without caudal. The eye is 
one-fourth as long as the head. The sides are covered by about thirty-three bony 
plates. The processes from the shoulder girdle cover the breast except a small naked 
area between them. At the base of each dorsal spine is a large rough bony plate to 
which the spine is hinged in such a way that it may be fixed and immovable at the 
will of the fish. The pelvic bone is lanceolate. A cusp at the base of the ventral 
spine. The spines are all closely serrated ; those in front of the anal and soft dorsal 
smallest. 
De Lk ty) bi-18 Ae ke 9: 
The living fish is greenish olive, lighter on the sides, the lower parts silvery. The 
gill covers are silvery with dusky spots; the iris silvery ; pupil black ; fins pale ; the 
ventral membrane sometimes red. 
The two-spined stickleback or burn stickle is found on both sides of 
the Atlantic, its range on our coast extending southward at least to New 
Jersey and northward to Greenland. This is the largest of the stickle- 
backs and is said to grow to a length of four inches. In the North 
Pacific and Bering Sea there is a related species, G. cataphractus Pallas, 
which has been styled the salmon killer. In Pennsylvania Mr. Seal has 
found this fish abundant in pools and ditches along the Delaware. 
Genus APELTES DeKav. 
112. Apeltes quadracus (Mircuitr). 
The Four-spined Stickleback. 
The body is fusiform in shape, the snout pointed and the caudal peduncle slender. 
The sides are somewhat compressed. The depth of the body equals the length of 
the head and is one-fourth of the total without caudal. 
DedMe Vy, 1, 1; A. 1,8. 
The skin is scaleless. The first dorsal spine is the highest, its length about half 
that of head. 
The living fish has the upper parts greenish brown. Below the lateral line the 
color is darker and is mottled by the extension upward of the white color of the abdo- 
men. Young specimens have the brown coloraggregated into several cross bands, 
which become indistinct in the adult. The ventral membrane is broad, scarlet in 
color, giving rise to one of the popular names. 
The four-spined stickleback is known in Great South Bay as the 
“thorn back.” In Massachusetts itis sometimes called the bloody stickle- 
back. 
This species reaches a length of two inches. It swarms in the shallow 
waters, especially in the northern portion of its habitat and is particu- 
larly plentiful in brackish streams where there are numerous aquatic 
plants. In salt marshes it is one of the commonest of the little fishes 
and it is not uncommon in the mouths of rivers. In Pennsylvania 
Prof. Cope records it as abundant in the tidewater streams and ditches of 
the Delaware. It is a beautiful fish for the aquarium. Its spinning 
habits have been described by Prof. John A. Ryder in the Bulletin of 
the United States Fish Commission for 1881. As a nest builder this is 
a most interesting species. 
