THE TANGANYIKA PROBLEM. 
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Nassopsis nassa, and Lithoglyphus zonatus , the first 
being supposed at the time to represent an aberrant form 
of the great tropical and sub-tropical family the Me- 
laniadce. Although nothing whatever but the shell was 
in his hands at the time, Woodward went further than 
this in the determination of the relationships of these 
molluscs, relegating Nassopsis to the sub-genus of the 
Melaniadce , Melanella. Subsequently, in 1880, a much 
more extensive collection of shells was brought to England 
by the captain of the small steamer which the London 
Fig. 1. — Back and front view of the shell of Melania admirabilis — Cerethinm 
subscalariforme. 
Missionary Society had put on the lake, and the still empty 
shells which were thus obtained were figured and described 
by Mr. Edgar Smith in 1881. Smith, like Woodward, 
drew attention to the extraordinarily marine aspect of 
these forms, specially pointing out the unique trochiform 
character of the shell of Limnotrochus , and the almost 
exact conchological identity which subsists between the 
shells of the Tanganyika Syrnolopsis and the marine 
genus Syrnola. Speaking of the curious marine appear- 
ance of these shells, Smith also drew attention to the 
