448 WEST INDIAN MOLLUSKS— SIMPSON. vol.xvii. 



During this the ishmd of Jamaica — as the character of its land-suail 

 fauna shows, as well as the depth of the channel between it and Haiti — 

 was lirst to be isolated, then Cuba, and afterwards Haiti and Puerto 

 Eico were separated. The connection between the Antilles and the 

 mainland was broken, and the Bahama region, if it had been previously 

 elevated above the sea, was submerged; the subsidence continuing 

 until only the summits of the mountains of the four Greater Antillean 

 islands remained above water. Then followed another period of eleva- 

 tion, which has lasted no doubt until the present time, and the large 

 areas of limestone uncovered (of Miocene, Pliocene, and Post Pliocene 

 age) in the Greater Antilles have furnished an admirable held for the 

 development of the groups of land snails that survived on the summits 

 of the islands. The Bahamas have ai)peared above the surface of the 

 sea, either by elevation or growth, and have been peopled by forms 

 drifted from Cuba and Haiti, and a number of land and fresh-water 

 species have been recently colonized in South Florida, i^robably since 

 the Glacial epoch. The Lesser Antilles have been peopled for the most 

 part from South America, possibly receiving from that region the group 

 CaprimiSj so characteristic of the former region, as well as several 

 genera of land operculates, while a few stragglers have been carried 

 by sea no doubt from the Greater Antilles and colonized on the more 

 northern of the Windward Islands. 



DESCRIPTIONS OF NEW SPECIES OF RECENT AND FOSSIL LAND 

 SHELLS FROM THE ISLAND OF JAMAICA. 



I. — Recent species. 



SAGDA MAXIMA, new species. 



Plate XVI, figs. 7, 8. 



Shell large, pyramidal in form, with nearly straight sides and obtuse 

 summit, moderately striated, and covered with a thin, horn colored 

 epidermis; Avhorls, 8^ to 9, moderately convex; suture distinct and 

 well impressed, sometimes slightly margined; last whorl wide, well 

 rounded; aperture large; base rather flat, not deeply excavated at 

 the umbilical region; the latter covered with a. light, glazed callous, 

 which joins the outer edge of the aperture. Interior entirely destitute 

 of a lamella. Greater diameter 30; lesser 27 mm,; height 28 mm. 

 !N"ear Petersfield, Westmoreland, on a mountain, in heavy forest. 



This si^ecies resembles 8. epistylioides somewhat, but has a broader, 

 less excavated base, and from one to one and a half less whorls, which 

 are wider than those of the latter, and the shell has not so pointed a 

 summit. Some 25 specimens (all dead) were obtained, varying from 



has brought shells from these beaches and submitted them to Dr. Dall, who pro- 

 nounces them to be Miocene, and probably of the same general age .as the Bowden 

 beds of Jamaica. It would seem most likely that the elevatiim and subsidence 

 would extend to some extent through the Bahamas and into the South Floridiau 

 regions. 



