Botany and Zoology. 135 
them there is a new genus called Stoastoma, characterized by a semi- 
circular aperture and projecting labrum, embracing as far as known, 
worthy of note—the latter forming a connecting link between the 
typical species of the genus and that most elegant of land-shells, the 
T. pagoda Velasquez, from the Isle of Pines. 
Of the 157 species of Jamaica Helicide, Prof. A. et Pesan 
more than 100, many of them of unusual beauty, and o ich we in- 
stance Cylindrella Agnesiana, Achatina elegans and the ttle it rep- 
resents, Helix peracutissima, H. fluctuata, H. virginea, &c. 
Professor Adams has also contributed much, price upon the import- 
ant subject of geographical distribution. ‘The most striking result pre- 
sented, is that while the marine species of the "West Indies are widely 
distributed, some few extending to Brazil, to our Southern States, and 
even to West Africa bam the Mediterranean, and not more than ten or 
fifteen per cent. bei liar to Jamaic a,—the case is quite the re- 
verse with the terrestrial shells, not more than six to nine per cent. of the 
Jamaica specie mmon probably to this and any other island 
will | ipeisaee os number of new and seoiitlay aie in at inate as 
great a proportion as of those common to other islands. These facts 
show that the field open to the conchologist in the tropical archipelagos 
is far wider than was ever su d. For if an examination of one 
tenth of ike surface of Jamaica has led to such results, how will our 
future catalogues be swelled with the lists of species still undiscovered 
on that island and the other great islands of Cuba, Hayti, a beget 
besides the many of smaller extent. And if this law holds true of 
different islands of the same group, how much more in regar hy proeye 
which are widely separated? It renders almost certain, what at one 
time would have been thought impossible—that the existing species of 
pt ei may far outnumber the marine spec ies. 
marks upon the different proportion in which certain genera 
of land shells are distributed i in the eastern and western hemispheres, 
