xviii Transactions of the Boyal Society of South Africa. 
Snakes," by W. Feei. Communicated by A. Theiler, F.E.S., South 
Africa. 
The author contends that from a toxicological standpoint the classifi- 
cation of the snakes in (1) Oglypha ; (2) Opistoglypha ; (3) Proteroglypha ; 
(4) Solenoglypha, is the most satisfactory. 
With regard to the question which of the doubtful South African 
snakes, chiefly Opistoglypha, are poisonous or harmless, only a preliminary 
answer can be given, owing to the experiments not being numerous 
enough. Five kinds of snakes were experimented with in that section. 
The difference in the postmortal lesions produced by the three venomous 
families of snakes are the following : Opistoglypha. — No pathological- 
anatomical alteration at all ; the poison is a simple one, a mere neurotoxine. 
Proteroglypha. — Local haemorrhages, slight haemolysis ; the poison con- 
sists of two components, a neurotoxine and a haemotoxine. Solenoglypha. 
— Local haemorrhages and necrosis, haemolysis. Besides the neurotoxine 
there is a strong haemotoxine which dissolves red blood corpuscles. It is 
yet doubtful whether the necrosis is due to a special component of the 
poison. Perhaps the haemolysine is able to destroy besides erythrocytes 
other cells like haemolytic sera which at the same time cause necrosis. 
" Note on a Theorem regarding a Sum of Differential-coefficients of 
Principal Minors of a Jacobian," by T. Mum. 
" An Upper Limit for the Value of a Determinant," by T. Mum. 
" Note on a Coenurus of the Duiker Bok," by L. H. Gough. 
The parasite was found imbedded in the muscles between the 
scapula and the vertebral column of a Duiker Bok [Cephalophus Grimmi). 
In view of the small number of intermuscular Coenurus recorded from 
ruminants a full description of the present one, which differs from Coenurus 
serialis, is given. 
" The Evolution of the Eiver System of Griqualand West," by A. L. 
DU ToiT. 
The drainage system in the area dealt with consists of the Orange 
Eiver with its tributaries, the Vaal, Harts, Eiet and Brak Elvers, sections 
of the first three forming the continuous valley facing the edge of the 
Kaap Plateau from Vryburg almost to Prieska. In Carboniferous times 
Griqualand West formed portion of a continent which possessed a river 
system draining in a southerly direction. This continent was glaciated, 
depressed, and finally buried beneath the sediments of the Karroo system. 
Intermittent elevation of South Africa during Cretaceous and Tertiary 
times enabled the rivers to cut plains of erosion or peniplains at various 
altitudes, the oldest and most important in this area being represented by 
the Kaap Plateau. The rivers have since cut down and laid bare in this 
area the floor of older rocks, and the development of the modern river 
system has been greatly influenced by reason of its superposition upon 
