594 UNITED STATES GEOLOGICAL SURVEY OF THE TERRITORIES. 



2. ampelita, Beck. 



Shell with last volution subangular around the umbilicus; peris- 

 tome reHexed, with margins contiguous, and united by a thin callus. — 

 {Helix Madagascar ~ensis, Lam.) 



H. and A. Adams admit the following three other subgenera under this 

 genus, viz, their own Lysinoe, Eurystoma, Albers, and Vallonia, Risso, all of 

 which, with the group Ampelita, Beck, are ranged by Albers as subgenera 

 under Helix. 



Not having studied these groups to any considerable extent, no great 

 weight is claimed for the conclusions here adopted with regard to their, 

 relations; but so far as I have had an opportunity to do so, the evidence 

 would seem to favor the conclusion that Lysinoe, Eurystoma, and Vallonia, 

 as well as possibly even Ampelita, should be kept entirely distinct from 

 Macrocyclis. 



In regard to the geological range of the genus Macrocyclis, little can be 

 said. If the species hereinafter referred to this genus really belongs to it, it 

 may probably be said to date back to the Eocene epoch. Although the 

 known existing species are not very numerous, it seems probable, from the 

 small number of fossil species yet discovered (including apparently a few 

 European Tertiary species), that it may not have been more abundantly 

 represented at any past time. It is possible, however, that a number of 

 Tertiary species may yet be discovered in the Rocky Mountain region and 

 along the Pacific slope. 



This genus has a wide geographical range, the typical section occur- 

 ring in Australia and Valdivia, and in this country from the Pacific slope 

 to Georgia. Mr. Tryon enumerates six species as occurring in the United 

 States and Territories, though Mr. Binney refers two of these to Zonites. 

 The species belonging to the group Ampelita are said all to occur in Mada- 

 gascar. 



Macrocyclis spatiosa, M. & H. 



Plate 42, figs. 9, a, b, c. 



Hdix spatiosa, Meek and Flayden (18G1), Proceed. Acad. Nat. Sci. Philad., XIII, 446. 



Macrocyclis spatiosa, Meek (18GG), in Conrad's Smithsonian Check -List N. Aru. Eocene Invertebrate 



Fossils, Id ; also (18G9),in Kinney's Land and Fresh-water Shells of N. Am., part I 



Pulmon. Geopliila, 168. 



Shell attaining a large size, thin, depressed-suborbicular, or subdis- 

 coidal, the spire being low, but not flat; volutions five and a half to six, 



