THE NAUTILUS. 39 
the shore. And on the extensive rocky coasts the barely submerged 
stones are covered with the so-called Lithoglyplus and Nassopsis, just 
as the half-tide rocks swarm with Natica and Litorina on an English 
beach. Further, on putting out into the lake itself, the deep open 
water is filled and discolored with clouds of pelagic Protozoa 
(chiefly Peridinia and Condylostoma) ; and during the dry season 
swarms of the lake jelly-fish are seen pulsating at all depths. 
“ Recapitulating, it may be said, then, that the facts of the geo- 
graphical and bathymetric distribution of the great lake molluscs 
lead to the following results :—That among all the fresh-water lakes 
of the African continent which have hitherto been explored there 
exists a type of fauna which is curiously similar throughout. It 
differs only in the specific representation of the same genera which 
these lakes contain. This generalized African lake fauna contains 
only those families and genera of molluscs which would be regarded 
as typically fresh-water, lake, river, and pond dwellers, in whatever 
continent the fresh-water might occur. In one African lake, how- 
ever, but in one lake only, there have been found to exist, super- 
added to this normal lacustrine stock, a number of Gastropods 
which do not closely resemble any other forms either living or extinct ; 
these molluses are also completely dissociated from the remaining 
normal series of the lake in which they occur by their modes of life. 
Together these molluscs constitute the molluscan section of a whole 
faunistic series, which in Tanganyike is added to the normal fresh- 
water stock the lake contains. This fauna forms what I have 
called the Halolimnic group, and the tout ensemble of all the Halo- 
limnic genera is marine.” 
The detailed anatomy of the Halolimnic genera is described in 
the second part of Mr. Moore’s paper. Typhobia and the allied new 
genus Bathanalia are extremely peculiar in many respects. The 
dentition resembles most that of the Strombide and Calyptrwide. 
The nervous system is most like Strombide, Cancellaria, Voluta, ete., 
with some peculiar features, and totally unlike any freshwater 
families. There isa crystalline style in the stomach, such as occurs 
in Pterocera. The external peuis is a new development in the 
mantle-wall. The gills are like those of Strombide. <A respiratory 
siphon is developed. On the whole, Typhobia and Bathanalia, for 
which the family Typhobiide is proposed, may fairly be held to be 
an old branch of the stock whence Strombide arose. 
