MOLLUSCA 



173 



various species are very difficult to determine. They 

 can be distinguished from Odostomia by an oblique 

 fold on the columella (shell axis). 



The most common New Jersey species are T. 

 conradi Bush and T. irderrupta Totten. 



Fig. 29 

 Polinices duplicata Say 



Polinices duplicata Say 



(Natica duplicata Say ) 



(Sea Snail; Moon Snail 

 Sand Collar Snail) 



PLATE XVIII. Fig. 11; Fig. 29 



A large shell (up to 3 inches in diameter) with 

 a comparatively flat apex; characterized by a thick 

 brown callus almost covering the umbilicus. Usu- 

 ally found partially buried in the sand from the 

 intertidal zone to relatively deep water; known 

 from Massachusetts to the Gulf of Mexico; common 

 in New Jersey. 



