THE NAUTILUS. 39 



the shore. And on the extensive rocky coasts the barely submerged 

 stones are covered with the so-called Lithoglyplus and Na$sopsis,ju$t 

 as the half-tide rocks swarm with Natlca. and Li tor in a 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 molluscs 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 Tanganyika 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 Strombidce and Calyptrceidce. 

 The nervous system is most like Strombidce, Cancellaria, Voluta,etc., 

 with some peculiar features, and totally unlike any freshwater 

 families. There is a crystalline style in the stomach, such as occurs 

 in Pterocera. The external penis is a new development in the 

 mantle-wall. The gills are like those of Strombidce. A respiratory 

 siphon is developed. On the whole, Typhobia and Bathanalia, for 

 which the family Typhobiidce is proposed, may fairly be held to be 

 an old branch of the stock whence Strombidce arose. 



LI ,RAI 



