FISHES OF CHESAPEAKE BAY 
47 
c. Labial folds wanting; teeth more or less serrate Carcharpinus, p. 48 
cc. Labial folds well developed, present on both jaws; teeth not serrate Scoliodon, p. 49 
5. Genus MUSTELUS Linck 
Body and tail of about equal length, rather slender; head short, broad, depressed; snout long 
and flat; spiracles small, behind eyes; eyes with a nictitating membrane; mouth small, crescent- 
shaped; teeth small, many rowed, pavementlike; dorsal fins similar in shape, the first above the 
abdomen, the second above the anal; caudal fin not deep, the lower lobe feebly developed; pectoral 
fins large. 
5. Mustelus mustelus (Linnaeus). Smooth dogfish. 
Squalus mustelus Linnaeus, Syst. Nat., ed, X, 1758, p. 235. 
Mustelus canis Jordan and Everraann, 1896-1930, p. 29. 
Galeorhinus Izvis Carman, 1913, p. 176. 
Body long, slender; head narrow, depressed, flattened beneath, about 4 in length; snout 
moderate, tapering, its length greater than the width of mouth; nostrils large, placed about half as 
far from the mouth as from the tip of the snout; eye rather small, its length about equal to the pre- 
narial length of snout, the pupil elongate horizontally, a nictitating membrane present; mouth 
about twice as wide as long; teeth small, numerous, pavementlike, in about 10 rows, the upper ones 
with a short and blunt cusplike projection on the posterior margin, lower teeth similar, with less 
Fig. 27 . — Mustelus mustelus 
prominent cusps, no cusps on teeth near angles of mouth; the skin roughened by rather large, sharply 
pointed denticles, bearing two or four low keels; origin of first dorsal a little in advance of the 
posterior margins of the pectorals; second dorsal inserted in advance of the anal, about half as large 
as the first; caudal fin about 4.5 in total length, the lower lobe scarcely produced; anal fin notably 
smaller than the second dorsal and inserted under the middle of the base of the second dorsal; ventral 
fins rather small, inserted nearer the origin of the anal than the base of the anterior rays of the 
pectoral; pectoral fins of moderate size, about two-thirds as broad as long, the hinder margins only 
slightly concave. 
Color usually uniform grayish, sometimes yellowish or olivaceous and with pale spots; pale 
underneath. 
The smooth dogfish previously has not been recorded from Chesapeake Bay. The present 
record is offered on the authority of the following field note made by Lewis Itadcliffe, at Gwynns 
Island, Va., May 6, 1915: “Among the fish brought in from pound nets in this locality and landed 
on the wharf was one smooth dogfish.” The same investigator also reports having seen a specimen 
at Buckroe Beach, Va. The foregoing description is based upon published accounts of the species. 
The food of the smooth dogfish consists mainly of the larger crustaceans. Field (1907, pp. 
11-13) examined the stomachs of 388 fish caught around Woods Hole, Mass., and found the principal 
foods to be lobsters, rock crabs, lady crabs, spider crabs, hermit crabs, menhaden, squid, razor 
clams, and Nereis. Besides menhaden, various species of small fish are eaten indiscriminately. 
“The eggs of this dogfish are fertilized internally, and the young are about 1 foot long when 
born. From 4 to 12 fish are produced at one time.” (Smith, 1907, p. 33.) A female examined by 
Linton at Woods Hole, Mass., contained eight young, each 12J£ inches long and ready to be born. 
