1865.] FALCONEE NILE AND GANGES. 375 



The structure of these bones was perfectly preserved, but the animal 

 matter had disappeared. Their surface was polished and of a 

 blackish-brown colour ; the substance very hard, but not yet petri- 

 fied"* (Jahrbuch, 1838, p. 403). In the second volume of his tra- 

 vels, published in 1843, Russegger enters at greater length into the 

 details of the^case, and states that the alluvial formation of the Blue 

 Nile, from Khartoom to Sennaar, consists of freshwater beds thrown 

 down by the river itself, and that, regarded as a whole, they are 

 divisible as follows, from above downwards : — 



1. Ordinary fluviatile mud, the result of modern periodical inun- 

 dation, analogous in its external characters to the Nile-mud of 

 Egypt, and containing imbedded nodules of calcareo-argillaceous 

 concretion (nodular kankar?). 



2. Friable, fine and coarse conglomerate, composed of quartz- 

 grains and pebbles, cemented by ancient mud, forming a kind of 

 sandstone -grit, and yielding calcareous and marly concretions. 



3. Ancient Nile-mud, indurated, and containing imbedded iron- 

 shot clay, siHceous limestone, &c., full of calcareous and marly con- 

 cretions in the ferruginotis portions. 



4. Fine and coarse quartzose conglomerate, with the materials 

 xmited by ancient Nile-mud and calcareo-argillaceous cement, very 

 hard, used as a building- stone, and containing imbedded masses of 

 saline clay and of ordinary clay and marl, full of clay-ironstone, 

 ferruginous sandstone, and of calcareoiis and marly concretions. 



5. Freshwater limestone (travertine, or slab kankar?) of a dark- 

 grey colour, hard and sonorous, occasionally having a marly appear- 

 ance, with here and there a tendency to a concentrical and generally 

 crystalline structui'e. 



The beds are described as horizontal, of very variable thickness, 

 attaining sometimes, in Nos. 1, 2, and 3, as much as five or six 

 fathoms (Jahrbuch, 1838, p. 408). According to Russegger, with 

 the exception of the uppermost deposit, they contain, very generally, 

 fossil vegetable remains, chiefly the wood of Mimosas (Mimosa 

 Niloticct) and stems oi Asclepia (Galotropis) procera : the former are 

 either converted into lignite or have their core exhibiting a con- 

 centrically disposed and radiating crystalline structure, derived from 

 the imbedding matrix ; the latter have the bark preserved, but the 

 spongy core occupied either by calcareous matter or conglomerate. 

 These alluvia presented very commonly shells of the Mollusca now 

 living in the waters of the Nile, both bivalves and univalves, to- 

 gether with some land species. Among the most common was 

 jEtheria CaUlaudi, occurring frequently in heaps or oj^ster-banks, 

 together with species of Unio, Iridina, and Anodonta. In the 

 alluvium of Sennaar he found Ampidlaria ovata and a species of 

 Helix. He adds, that JEtlieria Oailluudi was also abundant in the 

 deposits of the White Nile. 



* " In den AUuvionen des blauen Flusses bei Dundai fanden wir Menschen- 

 knochen. Das Gefiige der Knochen war vollstandig erhalten, der Tliiertnaterie 

 aber zerstoi't. Die Aussenflache war gliinzend und schwarz-braim gcfjirbt. Die 

 Masse sehi' hart, aber noch nicht versteincrt." 



