172 Bulletin American Museum of Natural History [Vol. LIII 
Pita Réding 
Pila Ropine, 1798, ‘Museum Boltenianum,’ IT, p. 145. Type: Helix ampullacea 
Linnzus, as fixed by Dall, 1904, Journ. of Conchology, XI, p. 53. 
Ampullaria Lamarck, 1799, Mém. Soc. Hist. Nat. Baie. p. 76. Monotype: 
Helix ampullacea Linneeus. 
Pachystoma GuILDING, 1828, Zool. Journ., III, p. 536. Type: Ampullaria globosa 
Swainson, designated by Guilding, op. cit., p. 539, footnote. (Not Pachystoma 
Latreille, 1809). 
Ampullaria subgenus Pachylabra Swainson, 1840, ‘Treatise on Malacology,’ 
p. 39. Type: Ampullaria globosa Swainson. Substitute for Pachystoma Guilding. 
Pachycheilus! . . . 1840, ‘Penny Cyclopedia,’ XVII, p. 454, footnote. Sub- 
stitute for Pachylabra SHON 
Pomus Gray, 1847, Proc. Zool. Soc. London, p. 148: Monotype: Helix ampul- 
lacea Linnezeus. 
b 
Fig. 14. Pla congoensis Pilsbry and Bequaert. a, penis with adjacent parts 
and section. 6, dorsal view, the mantle thrown to the left. 
br, end of the gill; Il, left epipodial lobe (respiratory siphon); Ir, longitudinal ridge; m, mantle; 
os, osphradium; rl, right or exhalent epipodial lobe; d, diaphragm; o, lung orifice; rt, right tentacle. 
Pachychilus Puiuipri, 1851, in Martini and Chemnitz, ‘Syst. Conch. Cab.,’ I, 
20, p. 7. Emendation of Pachylabra. 
Ampullariide with a dextral, ovate to globosely conic sheli and a rigid operculum 
having a strong calcareous layer inside. Left epipodial lobe short, capable of forming 
a very short, broad respiratory siphon. 
This genus is confined to the Oriental and Ethiopian Regions. In 
Africa it extends along the Nile into Lower Egypt, and is most abundant 
in the eastern and central portions of the continent. In West Africa it 
does not appear to have been found alive north of Lake Chad and the 
Niger, though subfossil specimens have been obtained in the dunes of 
Arezzal (Eroug, northern Sudan). In South Africa the southernmost 
1We have been unable to discover the author of the malacological articles in the ‘ Penny Cyclopedia.’ 
