THE TANGANYIKA PROBLEM \ 
265 
considered as generically distinct from Vivipara . The 
chief of these distinctions are found in the size of the 
animal, the remarkable characters of its shell, and in the 
arrangement of its nerves. 
In the nerves we find a very pronounced difference from 
Vivipara constituted by the existence of a strongly marked 
zygoneurous connection on the animal’s left side, while at 
the same time the cerebral ganglia are closely approximated 
together and the pleurals are applied to them below, instead 
of being separated from the cerebrals in the manner so 
characteristic of the Vivipara. (Compare Figs. 45 and 46.) 
Neothauma remains therefore generically distinct from 
Vivipara , but it is doubtful whether it should be regarded 
as a member of the Halolimnic group. 
Stanley a appears to be related to the nerilidae, and 
therefore is probably not a member of the Halolimnic 
group. 
