150 LEPAS, JCORN-SHELL. Class VI. 



10. spon- Mont. Test. Br. Sup. 2. tab. 17. /. 4. 5. 6. 



GEOSA. 



* L. with an ovate shell, and six wrinkled pointed 

 valves furnished with numerous spines ; oper- 

 culum of four valves, the anterior pair rough 

 with decussated striae ; length half an inch; 

 breadth less. 



VEXULA. 



ii. con- * L. with a smooth, truncated, subdiaphanous, 

 elliptic shell; operculum convex. This deli- 

 cate species, which I do not find described, is 

 very frequent on the coast of Anglesey, on rocks 

 and limpets ; the shell is evenly truncated ; its 

 height is not quite one half of its length ; aper- 

 ture very large; operculum regularly convex, 

 higher than the sides, smooth, unless there be a 

 faint stria on each side of the juncture of the 

 larger divisions of the operculum, each of the 

 ends of which form the segment of a circle; 

 and the juncture of them with the lesser parts 

 is transverse, and at about one fourth of their 

 length from the end ; the color of it is a faint 

 purple ; the size little more than the twentieth 

 part of an inch. Tab. xx,xviii. Jig. 2. much 

 magnified. 



