262 MRS. JANE LONGSTAFF ON NON-MARINE 



and size, but not in colour. S.fourtaiii is distinguished from S. uiarnoi in 

 being smaller, thinner, having the posterior dorsal margin slightly more 

 angular, the ventral margin more sinuated, and in the nacre being bluish or 

 greenish white instead of pink. 



M. Pallary does not state the exact locality on the White Nile where the 

 holotype was found. 



Family C Y R E N i D ^E. 

 Genus (;0RBICULA, Megerle von Miililfeldt. 



CORBICULA CONSOBRINA, CailUaud . 



Cyrena consobrina, Cailliaud, 1823, ' Voy. a Meroe,' vol. ii. pi. 61. figs. 10 & 11 ; 1837, 

 vol. iv. p. 263. 



This species occurred almost throughout the whole length of the river we 

 traversed. I took it near Mogran, at Ad-Duwem, Kosti, Abba Island, Hillet 

 Abbas, Gebel En, Mashra Zarafa Wood Station, Kaka, Hillet al-Nuwer, 

 Lake Shambe, south end of the Bahr el-Zarafa, and Gondokoro. It was 

 very numerous near Mogran and in Lake Shambe. Most of the specimens, 

 however, are immature ; the largest is a single valve from Hillet Abbtis which 

 measures, long. 34, alt. 30 mm. Another from Mogran measures, long. 23, 

 alt. 20*5. crass. 14*5 mm. The colour varies from lioht oreen in vouup- to 

 darker green, brown or nearly black in adult examples. C. consobrina exists 

 throughout the region of the Nile and in Abyssinia. 



CORBICULA ARTINl, PaUaviJ. 



Corbicida artini, Pallarj, 1902, 'Moll, recueillis par le Dr. Inues Bej dans le Haiit Nil,' 



Bull. Inst. Egypt, ser. iv. no. 3, p. 93, pi. 1. fig. 4. 

 Corhicula lavigeriana (Boui-guignat), Germain, 1906, Bull. Mus. Hist. Nat. Paris, p. 583, 



fig. 18 b. 



Only found in the Bahr al-Abyad, where it occurred at the following 

 places : near Mogran, at Ad-Duwem, Abba Island, Kosti, Hillet Abbas, 

 Masran Island, and Gebel En. It was most numerous at this latter place ; 

 a single valve taken there is the largest example, measuring, long. 23, 

 alt. 24 mm. A specimen from Tawila on Abba Island measures, long. 21, 

 alt. 21, crass. 15'5 mm. M. Pallary gives the dimensions as long. 22^ 

 alt. 23, crass. 18 mm. This is a remarkably solid shell ; the exterior varies 

 from pale green when young to dark rich brown when adult, the interior is 

 purple. M. Pallary states that this species is rarer at Alexandria and 

 Ismailia than in the White Nile. 



