FOSSILS OF THE WIND RIVER TERTIARY. 



MOLLUSCA. 



GASTEROPODA. 



PULMONATA. 



VITRINIDjS. 



Genus MACROCYCLIS, Beck. 



Synon.—Hacrocyelis, Beck (1837), Iud., 24 (proposed as a subgenus under Helix).— H. and A. Adams 

 (1855), Genera of Recent Moll., II, 202 (as a genus).— Cbenu (1859), Man. Conch., I, 

 461 (as a subgenus under Helix).— Morse (1864), Jour. Portland Soc. Nat. Hist., I, 12 

 (as a genus).— Tryon (1866), Monogr. Terrest. Moll. U. S., in Am. Jour. Conch., II, 

 244. — Binuey (1869), Land and Fresh-water Shells of N. Am., part I, Pulmon. Geo- 

 phila, 55. 

 Ampelita, Beck (1837), Iud., 30 (as a subgenus under Helix). — H. and A. Adams (1855), Genera of 

 Recent Moll., II, 203 (as a subgenus under Matrocyclis). — Chenu (1859), Man. Conch., 

 I, 461 (as a subgenus under Macrocyelis). 



Etym. — /janpiic, large ; kvkTmc, a circle. 



Type. — Helix laxaHi, Fe>uss. (= H. Peruviana, Lam.). 



Shell thin, widely umbilicated, depressed-orbicular, or subdiscoid; volu- 

 tions four to six, generally rather rapidly increasing in size, the last one 

 being inflated and declining at the aperture, which is transversely round-oval ; 

 peristome simple, thin, with margins approximated, and at the base shortly 

 reflexed, or contiguous and united by a thin callus. 



It will be seen that I accept this genus with two subgeneric sections, as 

 follows : 



1. macrocyclis, Beck (typical). 



Shell witli last volution rounding into the umbilicus; peristome 

 thin, with margins approximated, and at the base shortly reflexed. — 

 (Type as stated above.) 



593 



7."> n 



