THE TANGANYIKA PROBLEM. 
on what we now know about the prosobranchiate mollusca 
in general. 
TYPHOBIA, SMITH. T. HOREI (FIG. 2). 
The genus Typhobia is represented solely by the unique 
form T. horei which occurs generally in the deep water of 
Tanganyika, in a hundred fathoms and upwards, and on 
the muddy portions of the floor of the lake. The animal 
which is of considerable size possesses the remarkable shell 
represented on page 221, and the conchological characters 
which different individuals display may vary widely. 
Typhobia , like all the remaining halolimnic gastropods 
is prosobranchiate, and the mantle cavity presents the 
same arrangement of the parts which is usually found in 
the less specialised Taenioglossa, Aporrhais for example. 
There is one gill ( Stenidium ) composed of simple triangular 
leaves and below this a long rope-like osphradium (Fig. 3). 
The renal aperture is at the extreme upper end of the 
mantle cavity, and the intestinal and reproductive apertures 
open on the right, and on the extreme front of the mantle 
