52 
BULLETIN OF THE BUBEAU OF FISHEBIES 
10. Squalus acanthias Linnaeus. Spiny dogfish; Spiked dogfish; Grayfish. 
Squalus acanthias Linnaeus, Syst. Nat., ed. X, 1758, 233; coast of Europe. 
Squalus americanus Uhler and Lugger, 1876, ed. I, p. 191; ed. II, p. 163. 
Squalus acanthias Jordan and Evermann, 1896-1900, p. 54, PI. VII, figs. 24 and 24a. 
Body moderately slender, somewhat depressed anteriorly; caudal peduncle laterally with a 
low dermal fold; head low; snout pointed, 2.5 to 2.8 in head to first gill slit; its preoral part 1.75 to 
2.1 in head; mouth moderate, its width at angles 2.55 to 3 in head; eye lateral, elongate, 2.15 to 
2.25 in snout; interorbital space 2.3 to 2.8 in snout; teeth similar in each jaw, the cutting edges 
transverse, each tooth with a sharply pointed cusp, outer series in upper jaw with about 27 teeth, 
the lower jaw with approximately 22; longest gill slit 3.2 to 3.6 in snout; spiracles behind eyes, 
prominent; dermal denticles not imbricate, situated in more or less definite rows, each with a 
quadrangular base and a high median keel ending in a triangular apex; first dorsal rather small, 
preceded by a spine, the outer margin very slightly concave, its base 3.4 to 4.35 in space between 
dorsal fins; second dorsal smaller, with a larger spine, its base 4.4 to 5.6 in space between dorsal 
fins; upper lobe of caudal produced, no notch in lower margin, 4.6 to 5.35 in total length; ventrals 
inserted about equidistant from axil of pectoral and base of lower lobe of caudal; pectoral fins 
moderate, the posterior margin notab'y concave, 6.2 to 7 in total length. 
Color grayish above (occasionally brown), pale below, sides with small, roundish, pale spots 
in one or several rows, most prominent in young up to 14 inches, almost disappearing in largest 
fish. 
This shark is represented in our collection by six specimens — three males and three females — 
ranging in length from 560 to 800 millimeters (22 to 313dj inches). 
The spiny dogfish is a very voracious feeder. The stomach of one contained a partly digested 
squeteague, probably Cynoscion regalis, approximately 7 inches in length, and that of another 
contained a mass of partly digested fish, from which eight menhaden, ranging from 3 to 5 inches in 
length, were recognizable. The other specimens, having been taken in pound nets, were not 
examined. One of several fish examined in the field by us had eaten crabs and a small croaker 
(Micropogon). Bigelow and Welsh (1925, p. 49) give the food of the spiny dogfish as all fish 
smaller than themselves, squid, worms, shrimps, prawns, crabs, and at times even ctenophores. 
This shark is ovoviviparous. The large eggs, abundantly supplied with yolk, are at first in 
a horny capsule in the oviduct. Later the embryos break free, remaining in the oviduct or “uterus,” 
with which they have no placental attachment. The period of gestation has been variously esti- 
mated, but it appears that 10 to 11 months, based upon the studies of Ford (1921, pp. 468-505), 
is correct. 3 Ordinarily, a female gives birth to three or four young at one time, but the number 
may be only one or as many as eight to eleven. Gudger (1912, p. 143) records a specimen at Beau- 
fort from which three young were obtained. This fish was taken on May 23, but the size of the 
embryos was not given. Nichols and Murphy (1916, p. 32) state that spiny dogfish taken along 
the continental shelf off New York in late November contained well-developed young, the common 
number observed being three. They record a female taken near Gardiner’s Island, N. Y., June 12, 
1911, which gave birth to several young on the deck of the boat. We examined 12 specimens taken 
at Lynnhaven Roads, Va., April 4 to 8, 1922. Although selected at random, eleven were females 
and one was a male. The smallest fish (26 inches long) was the male. The length of the females 
and the number of embryos they contained are as follows: 
J For an account of the embryology see Bigelow and Welsh, 1925, pp. 49-50. 
