ON NON-MAEINE MOLLUSCA FROM THE SOUTHERN SUDaN. 233 



On a Collection of Non-Marine Molliisca from the Southern Sudan. By 

 Jane Longstaff, F.L.S. With Descriptions of Three New Species, by 

 H. B. Preston, F.Z.S. ; and Notes on Veronicella uilotica, by Gr. 0. 

 RoBSON, B.A. ^.---r — — ?-*^ 



(Plates 17, 18.) /^^"^ **" 



[Read 4th December, 1913.] 1 



Since many travellers in the region of the Upper Nile have collected f,»\\^^ 

 mollusca, which have been recorded either by themselves or others, it might--' 

 seem almost superfluous to write further on the subject. Unfortunately, 

 however, some authors have not been careful to give exact localities, while 

 others have founded new species on one or two specimens, or even on 

 immature ones. It may, therefore, not be devoid of interest to have an 

 account of a collection from the Sudan detailed both with reo-ard to localities 

 and numbers. 



This collection was made almost entirely on the White Nile, in the years 

 1909 and 1912. A visit each year to the mouth of the river near Mogran 

 was very fruitful, but still more so were two trips up the river in comfortably 

 equipped Government steamers. The first time we went, between the 16th 

 and 21st of February, we did not get further than Gebel En on the right 

 bank (lat. 12° 37' N.). The second journey took place between February 1st 

 and 23rd, and extended to Gondokoro in Uganda on the same bank 

 (lat. 4° 51' N.), and also about eight miles beyond to Rejaf on the opposite 

 bank (lat. 4° 45' N.), in the Lado Enclave, now forming part of the Anglo- 

 Egyptian Sudan. 



The distance traversed in steaming up the White Nile from Khartum 

 (lat. 15° 37' N.) was 1128 miles. North of Lake No (lat. 9° 30' N.) the 

 river is called Bahr al-Abyad ; it is fairly wide and the shores are more or 

 less shelving. South of Lake No, where the river is called Bahr el-Gebel, 

 we passed for many hours through the Sadd, which is composed of masses 

 of vegetation, much of it floating ; still further south the shores were usually 

 steeper, occasionally forming cliffs, while sometimes rocks cropped out in 

 the bed of the river. 



We went a little way up the tributaries Sobat and Bahr el-Zarfifa ; the 

 latter runs almost parallel with the Bahr el-Gebel, leaving it in lat. 7° 0' N., 

 and entering the Bahr al-Abyad in lat. 9° 25' N. 



In addition to collecting on the White Nile I had the opportunitv of 

 spending a few hours at Soba, about fifteen miles up the Blue Nile, in 

 lat. 15° 32' N., and also a short time at Khor Surkab, near Kerreri, on the 

 united rivers below Khartum, in lat. 15° 46' N. 



While ascending the White Nile numerous stoppages were made, and I 



LINN. JOURN. — ZOOLOGY, VOL. XXXII. 21 



