ODOSTOMIA. 295 



spire, whose nucleus is not inueh distorted, but sinks into 

 the apex, is composed of five or six rather high and convex 

 whorls, which are of slow longitudinal increase, and which 

 so arch inwards below as to appear abruptly divided by 

 the oblique and profound suture. The body, which is not 

 swollen in the middle, and is not angulated at the peri- 

 phery, has a gradual and convex basal declination. The 

 suboval mouth occupies from one-third to one-fourth only 

 of the entire length, and is a little produced or slightly 

 effused at the bluntly rounded anterior extremity ; the 

 posterior contraction is rather sudden. The peristome is 

 continuous in the adult. The edge of the acute and 

 merely convex outer lip, which is more inclined to curl 

 inwards than expand, is at first very indistinctly subsi- 

 nuated, then swells out, and finally again recedes. The 

 throat is quite smooth. The pillar lip, which is thin, 

 much elongated, and a little reflected, yet not appressed, 

 is but little arcuated ; the pliciform twist, with which it is 

 furnished, is distinct, but not striking. There is no umbi- 

 licus. The basal diameter of an individual that measured 

 fully two lines and a half in length, was only three-quarters 

 of a line. 



Still finer intermediate striula, that are parallel to the 

 longitudinal wrinkles, occasionally present themselves be- 

 neath the sutures. 



The refuse of the Plymouth trawl-boats furnishes us with 

 live specimens of this interesting species. 



