OF THE HALOLIMNIC FAUNA OF LAKE TANGANYIKA. 345 



Of the remaiiiiug genera of Gasteropods enumerated, none are especially 

 correlated with Jurassic forms, although they are regarded as belonging 

 to the halolimnic group. Syrnolopns is a genus of small elongate 

 shells represented by two species, and there is stated to be an almost 

 exact conchological identity (p. 219) between these shells and the marine 

 genus Syrnola. It is not necessary here to comment on all the remaining 

 halolimnic genera, consisting mostly of small forms, but I would point 

 out certain conclusions with reference to some of them, e.g., Rei/mondia, 

 Smith. There are several species, mostly small, but R. horei, Smith, is 

 the most conspicuous form, and may be taken as the type. I mention the 

 circumstance because of the very considerable conchological resemblance 

 between this very smooth shell and some of the Jurassic species such as 

 PhadanelW elegans, M. and L., and other sub-elongate forms. This 

 identification seems to have escaped Mr. Moore. I do not attach any 

 importance to it, since neither Reymondia horei nor " Phasianella " 

 elegans have any special features of ornamentation like Amberleya and 

 Purpurina. There is also another case of mock resemblance, where Horea 

 ponsonhyi., Smith, presumably a Prosobranch. bears a strong likeness to 

 some of the striated Actaeonince of Jurassic age ; whilst the remarkably 

 straight columellar lip of Horea reminds one of Orthostoma, which is, I 

 believe, a synonym of D'Orbigny's genus, Aciaeonma. 



Not the least interesting of the Tanganyika molluscs is the handsome 

 viviparoid shell, Neothauma, whose varieties are figured on p. 261. This 

 of course is a thoroughly fresh- water genus, and has no connection with 

 the halolimnic fauna beyond sharing the hospitality of the same lake. 

 One of the most remarkable characteristics of Neothauma is the extra- 

 ordinary difierence, judging from the figures, between shells from th 

 south of the lake, and those from the middle and the north. If the 

 internal structure is the same in all three, we have again an instance of 

 the difficulty of recognizing an animal by means of its shell even in living 

 creatures. Here again is a singular instance of mock resemblance to a 

 Jurassic species, since the strap-like or bicarinate variety of Neothauma 

 would also do for the figure of Cloughtonia cincta, Phillips, a well known 

 fossil of the Inferior Oolite of Yorkshire and the East Midlands. 



Postscript. This appendix was written before I had the advantage of 

 hearing Mr. Edgar Smith's presidential address to the Malacological 

 Society, delivered in February last. It was highly satisfactory to find 

 that the chief conchological authority in this country had arrived at 

 pretty much the same conclusions as myself, with regard to the presumed 

 connection between the halolimnic gasteropods of Tanganyika and certain 

 shells of the Inferior Oolite. 



