which inhabit Jamaica. 175 



shells can exist in this region. AVe are quite ignorant of the 

 manner in which this species was introduced to its habitat. 



Neritina Jainiaicensis. Shell obliquely ellipsoidal, rather 

 thin: white near the apex: otherwise covered with violet, 

 which is sometimes tinged with dark gray, with lighter and 

 darker shades in spiral bands, and is more or less interrupted 

 by lines of growth and irregular white spots: surface smooth 

 and shining: apex rather prominent: spire convex: whorls 

 nearly three, with a fine but well impressed sutural lino : la- 

 bium smooth, moderately thickened. 



Length of spire .07 inch ; height .3 inch ; breadth .32 inch. 



Neritina tenebricosa. Shell obliquely ellipsoidal, rather 

 thin: black, with numerous angular translucent spots of horn 

 color : white on the labium, blue within the aperture : with 

 numerous excessively fine spiral and incremental striie : apex 

 quite prominent: spire convex : whorls two and one-half, with 

 a very fine but well impressed sutural line : labium smooth, 

 moderately thickened. Inhabits Black River. 



Length of spire .06 inch ; height .36 inch ; breadth .41. 



It affords us much pleasure to find two new fluviatile spe- 

 cies of this genus in the Jamaica Fauna. With the excep- 

 tion of N. punctulata, all the other species are strictly marine, 

 living upon the open sea-shore. If authors are correct in 

 stating that St. Domingo is the habitat of N. punctulata, that 

 species is the only fiuviatile shell in Jamaica, belonging to a 

 genus of well characterized species, which is not peculiar to 

 the island. Possibly Lamarck's statement of habitat is erro- 

 neous, arising from the shells having gone to France by way 

 of St. Domingo. 



