252 HISTORY OF THE FISHES OF MASSACHUSETTS. 



The first dorsal fin is sub quadrangular, rather longer than high, deeply emarginated 

 posteriorly, and terminating in an acute point. 



The second dorsal fin is formed like the first, and is situated far behind it. 



The pectorals are large and subtriangular. 



The ventrals are subquadrangular ; the claspers on each side of the ventrals are as 

 long again as the fins themselves. 



The anal fin is of the same form as the second dorsal, but smaller ; it arises beneath 

 the middle of that fin, and extends beyond it. 



The caudal fin commences by a small elevation or crest, the prolongation, as it were, 

 upwards of the cuticle, gradually becomes higher and is rounded at its posterior ex- 

 tremity ; beneath, at its posterior extremity, is a triangular portion, which is partially 

 separated at its base by a small fissure from the anterior portion, which is of a more 

 elongated form. 



Length, two to four feet. 



Remarks. This species, which is called by the fishermen of Massachusetts Bay the 

 smooth hound from its smooth skin, and dog-fish from its general resemblance to the 

 dog-fish shark, I had not seen when my report on the fishes of Massachusetts was pub- 

 lished. Since then I have examined several specimens taken in our bay and at Holmes 

 Hole. This species sometimes runs ashore in great numbers. It is more numerous south 

 of the Cape. Its liver yields about as much oil as that of the Acanthias Americanus. 

 The largest I have met with measured forty-six inches. 



Massachusetts, Storer. New York, Mitchill, Dekay. 



GENUS IV. SELACHUS, Cuv. 



Two dorsal fins, — the first placed but little behind the line of the pectorals, the second 

 over the interval between the ventral and anal fins. The skin rough. Snout short and 

 blunt. Temporal orifices very small. Teeth very small, numerous, conical, edges 

 smooth, no lateral denticles. Branchial openings large, nearly encircling the neck. 



