Reference List of South African Non-marine Mollusca. 247 
Type in Zurich Museum. 
Hab. Ovampronanp. Ondonga (Schinz). 
DaMaraLAND. Okosongoho (Hermann). 
Brcnuanananp. Lake Ngami; Garu; fossil, south of Hardeko 
Drift, Botletle River (Passarge). 
British Becnuanauanp. Witkop (subfossil, Schultze). 
?CarE or Goop Horr. Port Elizabeth (fide Morelet). 
Considered by Béttger to be very near diaphana; Mousson’s 
figure, however, closely resembles angolensis, which is known from 
Angola and Damaraland. 
523. IstporA SERICINA, Jickeli. [S.A.M.] 
1874 Isidora sericina, Jick., Fauna N.-O.-Afr. p. 194. pl. 3, & 2p 7, 
foi, DEE 
1886 Physa 33 » Cless., Conch. Cab. p. 325. pl. 39 (1884), 
ie Igy 9 ale 
1898 . - » M.&P., Proc. Mal. Soc. iii. pzl82.  L. 
e »  schackor sr - be - Ke 
1908 Istdora sericina ,, Neuville & Anthony, Ann. Sci. nat. 
Paris, viii. pp. 274, 275. N.F. 
Type in Zool. Mus. Berlin. 
Hab. “Sourn Arrica” (in coll. Ponsonby). 
Care oF Goop Horr. Forty-eight miles from Port Elizabeth 
(‘‘ schackot,” in coll. Ponsonby). 
Described from Abyssinia. 
Careful examination of the two large series, on which the record 
of sericina and schackot from South Africa was originally based, 
proves them to contain only one species. Professor Thiele has 
kindly compared this with Jickeli’s types, and informs me that it is 
distinct from schackoi, but nearly allied to sericina, with which it 
may be identical. I have therefore removed schackoi from the South 
African list. Neuville and Anthony place sericina in the synonymy 
of contorta, Mich. The shells are certainly very similar, and might 
merge into one another, but Jickeli differentiated the two species by 
their radula, and, under these circumstances, it may be inadvisable 
to unite them without more extended investigation. 
524. Istpora TRoPICA (Krauss). [S.A.M.] 
1848 Physa tropica, Krs., Siidafr. Moll. p. 84. pl. 5, f.12. DF. 
1856s, ss »  Bgt., Rev. et Mag. Zool. viii. p. 236. D. 
- ty Fe % » Amén. malac. i. p. 175. D. 
