688 Modification of the Apex in Gastropod Mollusks. 



and a-half whorls, the second very rapidly enlarging ; a carina 

 commences on the last half of the second whorl and gradually 

 becomes stronger ; sutures deep but not channeled until the 

 second whorl appears. Color and texture as in volutella. Four- 

 teen perfect specimens have been examined, with no variation. 



Oliva hiatula Gmelin. (Fig. 8.) 



Apex rounded, smooth, shining, knob-shaped, but somewhat 

 elongated, consisting of two and a-half whorls, rapidly enlarging; 

 a carina begins on the last half of the second whorl, at first faint, 

 but soon becoming very strong ; the suture between the second 

 and third whorl is deeply channeled. Color bluish-black, hya- 

 line in texture. Two perfect specimens examined. 



Genus OLiIVEL-l-A Swainson. 

 Olivella Teuulata Lamarck. (Fig. 9.) 



Apex large, rounded, smooth, shining, knob-shaped, consisting 

 of one and a-half whorls rapidly enlarging, without a carina ; the 

 post-nuclear whorls are very flat-sided and the sutures deeply im- 

 pressed. The extreme apex of the present species is a good-sized, 

 rounded knob. Color and texture like spermaceti. Eight perfect 

 specimens examined. 



Olivella uiidatella Lamarck. (Fig. 10.) 



Apex large, conical, smooth, shining, consisting of three and 

 a-half rounded, regularly increasing whorls. The first whorl is a 

 little flattened, knob-shaped swelling and those following are more 

 or less turban-shaped. A carina is faintly perceptible on the last 

 half of the third whorl, and on the first post-nuclear whorl becomes 

 very strong ; the latter whorls also being deeply channeled at the 

 sutures. The color varies, in white specimens being like sperma- 

 ceti and in dark specimens shining smoky-black. The apex stands 

 up conically from the rest of the whorls and is easily seen with 

 the naked eye. Six perfect specimens examined. 



OliTella tergina Duc'os. (Fig. 11. ) 



Apex small, subconical, smooth, shining, consisting of two and 

 a-half rounded, rapidly increasing whorls. The first whorl is de- 

 cidedly knob-shaped and rapidly enlarges to meet the second 

 whorl. A carina begins near the suture above the third whorl, 

 encircles the second whorl of the apex and the first and second 

 post-nuclear whorls, and finally disappears in the adult whorls. 



