88 MANUAL OF THE MOLLUSCA. 
few in the extreme north), and each possessing many charac- 
teristic genera. 
America, Old World. America. Old World. 
Anastoma, Zonites. Choanopoma. Pomatias. 
Tridopsis. Nanina. Chondropoma. Otopoma. 
Sagda. Vitrina. Cistula, Craspedopoma. 
Stenopus. Helicolimax. Trochatella. Diplommatinga. 
Proserpina. Daudebardia. Alcadia. Aulopoma. 
Bulimus. Achatina. Stoastoma. Pupina. 
Odontostomus. Achatinella. Geomelania. Acicula. 
Liguus. Clausilia. — —_— 
Glandina. Paxillus. Hemisinus. Vibex. 
Cylindrella. Pupa. Melafusus. Pirena. 
Megaspira. — Ceriphasia. Melanopsis. 
Simpulopsis. Testacella. Anculotus. Paludomus. 
Amphibulima, Parmacella. Melatoma. Lithoglyphus. 
Omalonyx. Limax. - Amnicola. Navicella. 
— Arion. — — 
Philomycus. Phosphorax. Miilleria. ZEtheria. 
Peltella. Incilaria. ~~ Mycetopus. Tridina. 
— Oncidium. Castalia. Galatea. 
Chilinia. — Monocondylea. Cyrenordes. 
Gundlachia. Latia. Gnathodon. Glaucomya. 
The Land Provinces represented on the map are the principal 
Botanical Regions of Prof. Schouw, as given in the Physical 
Atlas of Berghaus; and it is proposed to inquire how far these 
divisions are confirmed by the land and fresh-water shells, more 
especially by the land-snails (Helicide, Limacide, and Cyclosto- 
mide), which have been s0 elaborately catalogued by Dr. L. 
Pfeiffer. * 
The first Botanical region—that of Saxifrages and Mosses— 
has not been numbered on the map, although its boundary is 
given by the line of northern limit of trees. This line nearly 
coincides with the Isotherm of 32°, or permanent ground-frost ; 
but in Siberia the pine-forests extend 15° farther, owing to the 
absence of winter rains and the bright clear air. 
In this region shells are very rare; Dr. Middendorff found 
Physa hypnorum in Arctic Siberia, and Limneea geisericola (Beck) 
inhabits the warm springs of Iceland. The few species dis- 
covered by Miller in Greenland are supposed to be peculiar :— 
Helix Fabricii. Succinea Greenlandica. Limnea Holbdllii. 
Pupa Hoppii- Limmea Vahiii. Planorbis arcticus. 
Vitrina angelice. » Pingelii. Cyclas Steenbuchii. 
* The distribution of the Cycladide is taken from the British Museum Catalogue, 
ty M. Deshayes. 
