Connection of Lake Tanganyika ivith the Sea. 



455 



proof of their oceanic character will more or less necessitate the idea 

 that the Tanganyika region of to-day mast have approximated in 

 character to an arm of the deep and open sea in ancient times. 



During my late expedition I was able to obtain sufficient material 

 for the complete morphological investigation of all the halolimnic 

 molluscs, the shells only of which have hitherto been known, as well 

 as for the two new genera Bathanalia and Bathoceras represented in 

 figs. 1 aud 2, and as I have worked over in detail a considerable number 

 of these forms I am now in a position to state definitely what they 

 really are. In 1857 S. P. Woodward, when describing the shells of 

 the so-called Litlioglyphus of Tanganyika, which had been obtained 

 by Speke, observed " the univalve .... so much resembles a 

 Xerita or Galyptrcea that it would be taken for a sea shell if its 

 history were not so well authenticated," and similar reflections 

 were made by other observers when describing the shells more 

 recently obtained by Captain Hore. 



But possibly owing to the weight then attached to Murchison's 

 geological speculations respecting the African interior, undoubtedly 

 to the fact that the Tanganyika jelly-fish was not then known, and 

 also because the fresh-water habitat of these molluscs was indisput- 

 able, the idea of their marine origin which was thus distinctly 

 before the minds of older zoologists subsequently became entirely 

 obscured. The shell of Typhobia was hesitatingly classed by 

 Smith in 1881, and more definitely by Fischer in 1887, with the 

 Melanidas* as a subsection of that group. The shells of the Para- 

 melanias were regarded as nearly related to the same, while the 

 really unique so-called Litlioglyphus of Tanganyika was equally 

 misplaced. The mere fact of the jelly-fish being, as I ascertained, 

 associated with other marine organisms in Tanganyika would throw 

 suspicion on these purely conchological determinations, and the 

 actual anatomical character of the halolimnic molluscs entirely con- 

 firms this view. The Typhobias are utterly unlike any Melania the 

 anatomy of which is known. These gasteropods in the character of 

 their radulae and their alimentary canals, in the presence of a crys- 

 talline style and an anterior stomachic ccecum, in the possession of a 

 well-developed posterior and anterior syphon, in the form of the 

 gills and osphradium, in the position of the anal, genital, and renal 

 apertures, as well as in the gross details of their reproductive 

 apparatus, most closely approximate to Strombus and Pteroceras. 

 The same inference may be gathered from the longi-commissurate 

 character of the nervous system, while in the absence of aright pallial 

 anastomosis, as well as in the form of the subintestinal ganglionic 



* In 1881 Smith became acquainted with the operculum of Typholia, which 

 seemed to confirm this opinion, but it is evident he doubted its correctness from 

 statements on the same page. (' Zool. Soc. Proc.,' 1881, p. 298.) 



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