MOLLUSCA FROM THE SOTJTHERX SUDAN. 235 



during the previous raiuy season. Those collected were all dead except a 

 single specimen of Veronicella nilotica, Cociv.;, found at Hillet al-Nuwer, a 

 small islet in the Sadd, and only one example of Limicolaria, which was 

 taken at Kakti, contained even a dead animal. No land-shells were seen 

 north of Abba Island (lat. 13° 22' N.), where we met with the first specimens 

 of Limicolaria, of which genus the individuals became more numerous 

 further south. Sheik Tombe, on the Bahr el-Gebel^, was the best place we 

 stopped at for land mollusca, but unfortunat'elj, after a violent thunderstorm 

 there were such torrents of rain that I was unable to go ashore. I was 

 therefore indebted to my husband and fellow-passengers for the specimens 

 obtained. 



The practice of setting fire to the vegetation in the southern districts was 

 most detrimental to the gasteropoda, and many were more or less calcined. 



No Lamellibranchiata were met with south of Lake Shambe with the 

 exception of immature specimens of Corbicula and Sphcerium at Gondokoro. 

 Possibly the steep character of the shores as well as my not havino- facilities 

 for deep-water dredging is answerable for this, since I always found bivalves 

 most numerous where the margin of the river was shelving. They were 

 especially abundant on the flat lower reaches of the Bahr al-Abvad, where 

 wading and other birds also abounded, and probably they afforded food for the 

 latter, for several shells taken had angular breakages as if made by birds. 

 On the muddy flats near Mogran specimens of Mtdela and Nodidaria were 

 very numerous. Quite the rarest species met with was Pseadomutela jMcata, 

 von Marts., of which I onl}^ obtained one example at Gebel Ahmad Agha. 



During the present century four collections from the Upper Nile have 

 been described, and in most cases accurate localities have been o-iven. 



The first was made by Capt. Flower, F.L.S., and recorded in the Proc. 

 Zool. Soe. 1900, p. 970. He obtained eleven species in the Bahr al-Abyad 

 and Bahr el-Zarafa, none of which was new to science. 



The second was the result of the Swedish Zoological Expedition to the 

 district between Shendi, lat. 16° 42' N., and Fashoda (Kodok), lat. 9° 54' N., 

 during the period from February until May in 1901. Twenty species and 

 four varieties were taken, and afterwards recorded by Herr Richard Haoo- 

 (1904). One of the latter, a variety of Limicolaria se nnaariensis, ^\\\\tt. 

 {flammata, Caill.), he regarded as new. 



The third collection was made by Dr. Junes Bey on the White Nile, and 

 described by M. Pallary (Bull. Inst. lEgypt. ser. 4, no. 3, March 1902). 

 Few of the localities visited are given, and the date is not stated. Twenty- 

 four species are enumerated ; two gasteropoda are not specifically denoted ; 

 three lamellibranchs are new, and two others, Unio euryssellinus, Letourn., 

 and U. nii/sticus, Bourg., have since been regarded by M. Pallary as varieties 

 of jyodukii'ia nilotica, Caill. 



21* 



