BIOLOGIA CENTRALI-AMERICANA. 
ZOOLOGIA. 
MOLLUSCA. 
A. SPECIES TERRESTRES. 
GASTROPODA PULMONATA DIOICA*. 
One pair of feelers, eyes at their base ; sexes separated; operculum rarely wanting. 
Fam. CYCLOPHORIDA. 
Operculum circular, formed of numerous narrow whorls, which give it the appearance 
of concentric structure. Shell depressed or globular, widely umbilicated, generally of 
simple, somewhat coarse sculpture and brown (pale yellowish to chestnut) hue, conco- 
lorous or with a single darker band; peristome straight or (in the American forms 
rarely) expanded. Size rather large. Regular Teenioglossata as regards the radula. 
The Cyclophoride have two centres of geographical distribution—one in the East 
Indies extending to Polynesia (more rich in distinct genera, especially some with com- 
plicated structure of the peristome), and the other in ‘Tropical America. In the latter 
their head-quarters is the tract of the Andes from Mexico to Ecuador ; some species are 
also found in Bolivia and on the east coast of Brazil and Guiana, and (a few) in the 
Caribbean Islands (about twenty, more especially in Jamaica), but there are none in the 
Nearctic Region. The two principal genera, Cyclotus and Cyclophorus, discriminated 
somewhat artificially by the structure of the operculum, are common to both hemi- 
spheres; but there are natural groups or subgenera within each, which are also 
geographically circumscribed. The subgenus Cyrtotoma is confined to Mexico, 
Amphicyclotus to the continent of Central and South America. 
* In the arrangement of the letterpress I have tried an innovation by summing up the conchological differ- 
ences of the species in a common table, instead of giving a separate diagnostical description of each at its 
place ; I believe the comparison and determination will thereby be rendered more easy, as by this method the 
common and the differential characters of the species are seen at a glance, without referring to different pages. 
In opposition to the “ clavis”’-like tables, which are usual in many handbooks, it has the advantage that the 
student may choose between five or six qualities in beginning the determination, and may take that which is 
the most striking or the least ambiguous in his specimen.—E,. v. M. 
BIOL. CENTR.-AMER., Terr. and Fluviat. Mollusca, May 1890. 1 
