174 Descriptions of Neiu Species and Varieties of Shells, 



represented by a variety which is more variable in size, and 

 the small mature specimens arc nearly intermediate between 

 var. minor and the common large type, which inhabits Man- 

 chester and otiier middle parts of the island. At Easington 

 in St. David's, is another variety, distinguishable from the 

 small specimens, which occur in the neighboring district of 

 Portland, by the entire absence of any internal lamina or 

 teeth. It may be called delaminata. 



The same name, delaminata, may be given to a variety of 

 H. osculans which wants the internal lamina. 



Proserpina nitida var. planulata is distinguished by be- 

 ing much flattened above. 



Descriptions of New fresh-ivater Shells which inhabit Ja- 

 maica. By C. B. Adams. April, 1851. 



Physa Jamaicensis. Shell long ovate, acuminate : brown- 

 ish horn color : wdth microscopic strife of growth, and some 

 lightly impressed microscopic spiral strisc : apex acute : spire 

 well lengthened, with the outlines slightly curvilinear, with a 

 well impressed suture : aperture long ovate : lip thin. 



Length of aperture .32 inch ; total length .48 inch ; breadth 

 .25 inch. 



This species was found plentifully in a tank at Malvern, 

 more than 1000 feet high, in the isolated group of the St. 

 Cruz Mountains in St. Elizabeth. The structure of the coun- 

 try for many miles in every direction is such that no water is 

 ever seen standing on the surface. Through innumerable sub- 

 terranean fissures rain immediately percolates to unseen depths. 

 Artificial tanks are therefore the only places where fresh water 



