Fishes of Massachusetts. 545 
ach filled with a species of the genus “ T'alitrus," 
Beach flea. 
The sexes are readily distinguishable by the 
ventral fins. From the ventral fins in the male, ex- 
tends a cylindrical appendage about half the length 
of the tail, measuring from the anal orifice, which is 
called the clasper ; at its posterior, outer portion, it 
is fissured, and contains on its lower division a large 
faleiform bony hook, and on the upper, a small pro- 
jecting tooth, somewhat like a shark's tooth; the 
ventrals of the female have not these appendages. 
Besides this serual character, there are, in the fe- 
male, fewer spines upon the surface of the body gen- 
erally, ahd particularly upon the fleshy portions of 
the pectorals. The anal orifice of the male, is circu- 
lar; of the female, a simple incision ; the teeth of 
the female are more prominent, and sharper; the 
male has fewer spots. 
R. batis. Lin. The Skate. 
Pennant's British Zoology, vol. iv. p. 72, et hg. 
Mc Murtrie's Cuv. vol. ii. p. 293. T 
Yarrell’s British Fishes, ki ii. p. 421, et fig. 
This species sometimes attains the weight of 200 
pounds. From a female specimen, three feet three 
inches in length, and two feet in width from the 
extreme points of the pectorals, brought me by my 
zother-in-law, Thomas M. Brewer, M. D., I have 
made the following description : 
Above, of a light ash color, sprinkled over its 
VOL. IL—NO. I—IV, 51 
