FISHES OF MASSACHUSETTS. 187 



At the base of the fleshy portion of the Caudal fin, a de ep 

 groove on each side, running half the length of this portion. 

 Caudal fin unequal in its lobes ; the upper, measuring along its 

 curve, twenty-three inches ; the lower, eighteen. Depth of 

 the caudal fin at its extremities, two and a half feet. 



Near the anus, imbedded in the flesh, I found a specimen of 

 the '' Atithosorna Sniithii^' — Leach. 



Large specimens of this shark, which is usually found only 

 three or four feet long, have been mistaken for the '^Carcharias 

 glaucus^' — Blue Shark — by our fishermen. Although the 

 Blue Shark may exist in our waters, still as I have not been 

 able to meet with it, nor with any one who has seen it, upon 

 whose scientific accuracy I can implicitly rely, I have erased 

 it from our catalogue, and substituted this species. The re- 

 marks made in my former report are applicable here, and are 

 therefore introduced. 



Spinax. Cuv. 



Generic characters. Two dorsal fins, luith a strong spine at 

 the anterior edge of each ; no anal fin ; temporal orifices pres- 

 ent ; teeth in several roios, small and cutting. 



S. acanthias. Lin. The picked Dog-fish. 



Pennant's British Zoology, vol. iv. p. 88. 

 Shaw's Zoology, vol. v. pt. ji. p. 33. 

 ' Mc Murtrie's Cuv. vol. ii. p. 288. 



Yarrell's British Fishes, vol. ii. p. 400, et fig. 



This species is known in Great Britain by the name of 

 ^^ Picked or Piked Dog," from the strong spine at the com- 

 mencement of each dorsal fin. Oar fishermen called it " Dog- 

 fish." In the spring and autumn, the dog-fish appear in 

 shoals in our bay ; they are frequently met with in immense 

 numbers. At their appearance, smacks are fitted out at Truro 

 and Provincetown for their capture, to the neglect of other 



