256 HISTORY OF THE FISHES OF MASSACHUSETTS. 



GENUS V. ACANTHIAS. Eisso. 



Two dorsal fins, with a spine before each ; first dorsal behind the line of the pectorals ; 

 the second dorsal over the space between the ventral and caudal fins ; no anal fin. 

 Skin rough in one direction ; the scales heart-shaped, with a central spine directed back- 

 ward. Temporal spiracles large. Several rows of teeth in both jaws, cutting and sharp, 

 the points directed outward and backward. 



ACANTHIAS AMERICANUS, Storer. 



The Dog-fish. 



(Plate XXXVIII. Fig. 1. 1 a. Jaws.) 



Spinax acanthias, Picked Dog-Jish, Storer, Report, p. 187. 



" " Spinous Dog-Jish, Dekay, Report, p. 359, pi. 64. 



" " Dog-Jish, Ayre8, Bost. Journ. Nat. Hist., iv. p. 289. 



Acanthias americanus, Stores, Synopsis, p. 606. 



Color. All the upper part of the body is of a slate color, which is deeper upon the 

 head, and fighter below the lateral fine. Body beneath, white ; a row of circular white 

 spots are situated just under the anterior portion of the lateral line, and a few similar 

 spots are irregularly distributed upon the back ; these spots, in some specimens, are 

 arranged with much more regidarity than in others. The young of this species are 

 much more spotted than the adults. In several foetuses I have examined, there have 

 been noticed several white spots on the tops of the shoulders, — two in front of, and two 

 just behind, the first dorsal fin ; also spots on the sides, which, becoming confluent, form 

 a white band extending almost the whole length of the body. 



In a male specimen, twenty-three inches in length, I could scarcely observe a spot 

 upon its entire surface. 



Description. Body elongated, cylindrical, with a slight ridge on the back, which is 

 more perceptible between the dorsal fins. A distinct carina on each side of the abdo- 

 men, posterior to the second dorsal fin. The entire surface is rough. The head, which 

 is flattened above, and tapers to a blunted snout, is equal to one seventh the entire length 

 of the fish. The eyes are horizontally elongated; the pupils are small, black; the irides 

 are silvery with a cupreous tint. The orbits are large, allowing great motion to the 

 eyes. The distance between the eyes is equal to more than one half the length of the 

 head. The temporal orifices are back of, and just above, the posterior angles of the 



