116 3 Bulletin American Museum of Natural History — - [Vol. LIII 
and the shell in its early stage (and in some adults) is obviously sinistral. 
The shell is sometimes carried with its disk approaching a vertical posi- 
tion; but in the flatter forms it is carried horizontally, the left side below, 
in which case the spire (speaking morphologically) is beneath. 
The genus is cosmopolitan in its distribution. Of the many sub- 
genera into which it has been divided, only three, namely Planorbis, 
proper, Gyraulus J. de Charpentier, and Hzppeutis J. de Charpentier, 
appear to be represented in the Ethiopian Region, at least on the con- 
tinent.!. In the Island of Sokotra, however, the two following species 
represent two other subgenera which have not yet been recorded from 
Africa proper. | 
Planorbis exustus Deshayes var. maculatus GODWIN-AUSTEN, 1883, Proc. Zool. 
Soc. London, p. 3, Pl. 1, figs. 1 and la-b. Both Crosse (1884) and E. A. Smith (1903) 
unite this variety with the typical form of Planorbis exustus Deshayes, an Indian 
species for which Annandale and Prashad have recently erected the genus Indoplan- 
orbis (1920, Indian Jl. Med. Res., VIII, p. 118 and 1921, Rec. Indian Mus., XXII, 
_ 578). | 
: Eine socotrensis GODWIN-AUSTEN, 1888, Proc. Zo6l. Soc. London, p. 3, PI. 
1, figs. 8 and 3a-c. This appears to belong in the subgenus Tropidiscus Stein. 
No doubt several genera will soon be generally accepted in place of 
the heterogenous Planorbis, but at present we have only conchological 
data on the African forms. : 
The species of tropical and southern Africa are of moderate or small 
size, never reaching the dimensions of some of the American or European 
forms. | 
_ Subgenus PLANORBIS, proper 
Shell relatively large and thick, regularly discoidal; equally umbilicate on both | 
sides, with relatively few whorls which are convex above and below; aperture oval 
or rounded. , 
This subgenus is found in Europe, Asia, Africa, and Madagascar. 
The subgenotype is the same as the genotype, Planorbis corneus 
(Linnzeus). 
The following Ethiopian species have generally been referred to 
Planorbis proper. , 
Planorbis adowensis Bourguignat. See p. 118. 
Planorbis adowensis var. major GmRMAIN, 1908, in A. Chevalier, ‘L’ Afrique 
Centrale Frangaise,’ p. 508. Mamun country. 
Planorbis adowensis var. problematicus GERMAIN, 1908, in A. Chevalier, ‘L’ Afri- 
que Centrale Francaise,’ p. 508. Gribingui River, Chad Territory. 
SS eee ent Sai TH PA EWP J] Use Oe eter Ah IWS VAR Os FEMS ED Oot SOG Emer SAL SARK SATs) PPT tay Oe ne ae a 
1In the following lists of Ethiopian species we have disregarded the numerous forms which have 
been named from Lower Egypt. Planorbis’ caffer ‘“‘ Krauss’? Moreuet, 1889, Journ. de Conchyl., 
ecie oe p. 19, listed from Port Elizabeth, Cape Colony, is a nomen nudum and probably due to a 
clerical error. ne 
