130 



convex, with a well impressed suture : aperture ovate orbicu- 

 lar, with two peritremes, of which the outer one is moderately 

 expanded and reflected nearly into the plane of the aperture ; 

 the inner one is moderately produced and reflected : umbilicus 

 very narrow, but extending through the truncate summit. 



Mean divergence about 37° ; length after truncation .54 

 inch : greatest breadth .34 inch ; least breadth .23 inch. 



From Easington. At first sight this species appears like 

 C. Adamsi, but is distinguished by being less elongated, by 

 the spiral striae, and by the double peritreme, 



Cyclostoma tenuistriatum is frequently of a dingy white or 

 very pale brown color. 



Cyclostoma modestum Ad. (Cont. Conch.) 



A variety of Cyclostoma fimbriatuliim has the transverse 

 ridges rather more numerous and regular than the type of the 

 species, and at their intersection with the spiral ridges more 

 or less developed into small opaque white tubercles : its outer 

 peritreme is not so wide or scabrous, and is less strongly scal- 

 loped, and is less flattened. Its size is less than that of the 

 type of the species. It is a local variety, occurring in the 

 centre of Westmoreland, the most western" parish, while the 

 typical C. fimbriatulum occurs forty miles to the east, in Man- 

 chester, near the centre of the island. At the suggestion of 

 Mr. Chitty, I propose for it the name of albinodatum. 



Another variety of the same species inhabits an interme- 

 diate region, the parish of St. Elizabeth's. Yet although ge- 

 ographically intermediate between the other two forms, it is 

 by no means so in its characters. It is smaller than the var. 

 albinodatum, has its peritreme narrower, and the transverse 

 ridges are more numerous and regular, in these characters 

 diverging yet farther from the type of the species. On the 

 other hand, it diverges in the opposite direction, having the 



