352 HELICINAD.E. 



Trochidse. Mr. Gray makes a family exclusively for 

 them, which he calls Oligyradge ; but it would not seem 

 that their anatomical characters are sufficiently diverse 

 from those of Cyclostoma to justify a separation. [G.] 



1. HELICINA ORBICULATA, SAY. 

 PLATE LXXIII. LXXIV. FIGURE 3. 



H. testa parva, sub-globosa, solidula, tenuissime striata 

 flavescente, cinerascente, vel rufescente, plerumque ad peri- 

 pheriam albo-zonata ; spira anfractibus quinque, convexis ; 

 apertura lunata ; labro reflexiusculo, albo, incrassato, junc- 

 tione cum columellam dentiformi. 



SYNONYMS AKD REFERENCES. 



Oligyra orbiculata, SAY, Journ. Acad. Nat. Sc. I. 283, May, 1818 ; 



Nicholson's Encycl. IV. ; 



American Conchology, pi. 46, figs. 4, 5, 6. 

 Helidna orbiculata, GRAY, Zo6l. Journal, I. 70. 

 Ilelidna rubella, GREEN, Doughty's Cab. Nat. Hist. II. 291, anno 1832. 



DESCRIPTION. 



ANIMAL. Head and tentacles black, the other parts 

 of the body dark. Tentacles long and slender, tapering 

 to a point. Eyes black and prominent. Motion gliding 

 as in Helix. Operculum horny, turning back upon the 

 colurnella as if upon a hinge. 



SHELL. Shell sub-globose, acute at apex, solid, 

 smooth, very delicately striated ; color yellowish, brown- 

 ish, or ash-colored, with a linear, pale zone at the peri- 

 phery, which passes up the spire at the suture, and 

 makes it white ; there are also in many specimens 



