16 CONTRIBUTIONS TO NORTH AMERICAN ICHTHYOLOGY IV. 
10.— CEWTROSCYI.I.IUM Muller & Henle, 1837. 
Black Dog-fishes. 
(Mliller & Henle, System.-xtische Beschreibung der Plagiostomen, 191 ; type Spinax 
fabricii Reinhardt. ) 
Teetli equal in botli jaws, very small, straight, pointed, each with one 
or two smaller cusps on each side at base ; mouth crescent-shaped, with 
a straight, oblique groove at its angle ; spiracles moderate j gill-open- 
ings rather narrow 5 dorsal fins small, each with a strong spine ; the 
second dorsal entirely behind the ventrals. One species, {xivrpov, spine ; 
ffxoUtov^ Scglliuni, an allied genus, from cxuXXojj to rend or tear to pieces.) 
15. — C. fabricii (Reinhardt) M. & H. — Black Dog-fisTi. 
Body covered with minute stellate ossifications ; color dark brown. 
A shark of the Greenland Seas, lately taken off Gloucester, Mass., by 
the United States Fish Commission. 
(»Sj)fnax/a6ncH Reinhardt, Dansk. Vid. Selsk. Forh. 1828, iii, xvi; Gunther, Auii, 425.) 
k 
II.— SQUAEUS Linnajus, 1758. 
Dogfishes. 
(Acanthias Risso.) 
(Artedi, Linnaeus, Systema Naturae ; type Squalus acanthias L.) 
Body rather slender ; mouth little arched, with a long, straight, deep, 
oblique groove on each side 5 no labial fold along the margin of the 
mouth ; teeth rather small, equal in both jaws, their xioints so much 
turned aside that the inner margin forms the cutting edge ; spiracles 
rather wide, just behind the eye ; gill-openings narrow, in front of the 
pectorals ; fins moderately develoiied, the first dorsal larger than second, 
much in advance of the ventral fins, which are behind the middle of the 
body, although in advance of the second dorsal. Small sharks, abound- 
ing in the Temperate Seas. (Latin, squalus, a shark.) 
* Dorsal spine uot grooved ; its insertion rather behind inner angle of the pectorals. 
16. — sicuntliias L. — Picked Dog-fish ; Dog-fish; Bone Dog ; Skittle-dog; Hoe. 
Body slender; snout pointed; head in length; depth about 8; 
slate-color above, pale below, back with whitish spots, especially in the 
young. L. 1 to 3 feet ; weight 5 to 15 pounds. 
A small sharp-toothed shark, ranging widely in the Atlantic, very 
abundant along the shores of the Northern and Middle States. It is 
somewhat valued for its livers, from which “Dog-fish” oil is extracted. 
American writers have usually considered our siiecies {Squalus ameri- 
