133 



lusca of the Island of Jamaica, with remarks on their geo- 

 graphical distribution and habits, extended descriptions of 

 newly-observed species, and remarks on those already 

 known. 



The materials, from which Mr. Adams prepared this paper, 

 were collected by him, personally, during a visit to Jamaica, in 

 the winter and spring of 1843 and 1844. The portion of the 

 island explored was but small, comprising the Bay of Port Royal 

 only on the south shore, and the coast from Annatto Bay, inclu- 

 sive, to Rio Bueno, a distance of sixty miles, on the north ; and, 

 in the interior, the region between Kingston and Spanish Town, 

 on the south, and Annatto Bay and GaHna Point, on the north. 



The author states that the differences in the terrestrial species 

 occupying the sandstone, and limestone, districts respectively, is 

 very striking, and the transition instantaneous. Cyclostoma, 

 Helicina and Cylindrella are restricted to the limestone district, 

 as also the larger species of Bulimus, Achatina, Pupa and Helix ; 

 while the minuter species of the latter genera, and Siiccinea^ are, 

 for the most part, common to both. The bases of perpendicular 

 limestone cliffs, and cavernous limestone rocks, were invariably 

 found to afford immense numbers of land-shells. Such places 

 are the favorite retreat of the Colimacea, during seasons of 

 drought ; and here great numbers of their shells were collected. 

 The marine species, inhabiting a rocky station, are also most 

 abundant on limestone rocks. These rocks are worn by the 

 waves into irregular cavities of various dimensions, which afford 

 shelter to multitudes of them. 



The profusion in which these animals are distributed, in favor- 

 able localities, is shown by the fact that, near a place called 

 Goshen, Prof Adams obtained forty terrestrial species, within 

 a circuit of two miles in diameter, and on the inner side of the 

 peninsula, one hundred marine species, within a space of two 

 miles from Port Royal. 



One of the causes affecting the increase of the terrestrial 

 species, and, at the same time, affording a curious instance of the 

 indirect influence of human agency in disturbing the equilibrium 

 of species, is stated to be their frequent destruction by rats. The 

 cultivation of the coffee plant tends to the excessive multiplication 



