MOLLUSC A OF PORTO RICO. 
357 
Another striking feature of the land-snail fauna of the region is the presence of 
large, generally dark-colored and solid snails of the genus Pleurodonte. They are 
all ground snails; they are usually abundant, and are probably found in all the sub- 
regions of the West Indies region. Another great and characteristic group, which, 
like Pleurodonte ^ has its metropolis in this region, is the old genus Oylindrella , but 
which is now divided into several genera forming the family Ueocoptidw. 
The land-snail fauna of Porto Rico is not especially striking, though there are 
a few very line large species of Pleurodonte , notably P. carocolla , P. angulata , P. 
luquillensis , and P. marginella. The latter, or a closely related form, is found also in 
the islands of Haiti and Cuba. 
The solitary Gircinaria eoncolor , if it be a genuine Circinaria , is a remarkable 
case of geographical distribution, all the other species being confined to the United 
States. Equally remarkable is the single Olausilia bicanalicidata , which is found only 
in Porto Rico, there being no other species of the genus known from the West Indian 
region. The genus has its metropolis in southeastern Europe, where both species 
and individuals are very abundant. It is represented by numerous species in Eastern 
Asia, by a few in the Malay Archipelago, the Madeira Islands, and along the west 
coast of South America. 
There is a single species of Stoastoma found in Porto Rico, another comes from 
Haiti, and about 80 species are found in Jamaica. All the species are minute, the 
largest being less than 5 millimeters in diameter. Pineria riequenxi* comes from the 
island of Vieques, but has not, so far as we know, been reported from Porto Rico. 
Two other species belong to Cuba and the Isle of Pines, and another is found in 
the Lesser Antilles. The genus Gceotis, with four species, the animal being large, 
broad, and depressed, with a fragile sigaretiform shell, is confined to the island of 
Porto Rico. There are a number of species of Helicinci , Cistxda , Ghoanoponui , and 
Ghondropoma in the island, but they have no remarkable characters. Planorbin and 
Planorbulu are largely represented, there being no less than ten species of the two 
genera. 
In his account of the land and fresh-water mollusk fauna of Haiti, 1 Crosse 
divides the island into four subregions, as follows: First, that of the Sierra de Monte 
Cristo on the north, extending from Monte Cristo on the west to the Bahia Escocesa 
on the east. South of this there is a wide subarid plain. Second, the region of the 
Sierra del Cibao, extending' from the Mole St. Nicholas on the west to Cape Engano, 
the extreme eastern end of the island. There is a third subregion extending from 
Cape Dame Marie, the extreme southwest point of the island, eastward to beyond 
the center of it, and a fourth lying between the two western peninsulas. The sub- 
region on the southwest peninsula has a land-snail fauna closely allied to that of 
Jamaica; that of the Sierra del Cibao, which reaches from the extreme northwestern 
point to the eastern end, has a fauna which is much like that of eastern Cuba, and 
also much like that of Porto Rico. It is in this region of the Sierra del Cibao that 
the large, dark Pleurodontes are found, which are closely related to forms of the 
same genus in eastern Cuba and to those of Porto Rico. In fact, Pleurodonte 
marginella , or very closely allied forms, are found in eastern Cuba, throughout the 
1 Joum. de Conch., xxxix, 1891, p. 195. See also the same, xi.. 1892, p. 54. 
