NASSARIIDAE 237 



part of the Gulf of Mexico, specimens often have a weak keel on the 

 shoulder (form or subspecies plagosum Conrad). 



Busy con coarctatwn Sowerby Turnip Whelk 



Plate I a 



Yucatan area, Mexico. 



Until 1950 this was considered a very rare species, but dredging activities 

 of shrimp trawlers have brought a large number of them to light. Charac- 

 terized by its turnip-like shape, single row of numerous small, dark-brown 

 spines, and by its golden-yellow aperture. 5 inches in length. 



Family NASSARIIDAE 



Genus Nassarms Dumeril 1806 



Subgenus Nassarms s. str. 



Nassarms vibex Say Common Eastern Nassa 



Plate 2 3q 

 Cape Cod to Florida, the Gulf States and the AVest Indies. 



% inch in length, heavy, with a well-developed parietal shield. Last 

 whorl with about a dozen, poorly developed, axial ribs which are coarsely 

 beaded. Color gray-brown to whitish with a few splotches or broken bands 

 of subdued, darker brown. A common sand or mud-flat species. Some 

 specimens have numerous weak spiral cords. Parietal shield sometimes yellow- 

 ish. 



Nassarms acjitus Say Sharp-knobbed Nassa 



Figure 53c 



West coast of Florida to Texas. 



Ya: inch in length, characterized by its glossy shell, its strong, pointed 

 beads, and in occasionally having a narrow, brown, spiral thread connecting 

 the beads. Moderately common. Fossil specimens are twice as large. 



Nassarms insculptus Carpenter Smooth Western Nassa 



Figure 53f 



Point Arena, California, to Lower California. 



% inch in length, outer lip thickened, parietal wall thick, white but 

 not very wide. Body whorl smoothish, except for weak, fine spiral threads. 

 Axial ribs numerous only on early whorls. Color white, covered by a yellow- 

 ish white periostracum. Moderately common; dredged from 20 to 200 

 fathoms. 



