182 ANIMALS OF THE SEASHORE 



Triphora perversa nigrccincta C. B. Adams 



Fig. 28 H 



Shell black, about % inch long. This species is 

 easily recognized because it is sinistral or left- 

 handed — that is the whorls turn to the left and the 

 opening- is on the left side. Cape Cod to Florida; 

 rare in New Jersey. 



Bittium alternatum Say 



(B. nigrum Totten; Diastoma virginica Henderson & 

 Bartscli 



PLATE XX. Fig. 10 



A right handed shell about Vi? inch long; 

 rounded aperture; often abundant in shallow water 

 Massachusetts to North Carolina. 



Urosalpinx cinerea Say ( Oyster Drill ; Drill ; Borer ) 



PLATE XX. Fig. 8 



These gastropods bore small round holes in 

 shells, pa idarly those of the young oyster. They 

 are found in great numbers in Delaware Bay where 

 they cause considerable damage to the beds in 

 Maurice River Cove. They are especially abundant 

 below low tide, although they may sometimes be seen 

 alive on the exposed beach or mud flats. They are 

 not as resistant to fresh water as the oyster and are 

 therefore not common in the upper part of Delaware 

 Bay and are rare above Fortesque. Drills are also 



