306 J. E. S. MOORE. 



1. That in the genera Bathanalia and Typhobia we 

 have a type of Gasteropods which stands very much in the 

 same relation to the modern Strombidse that the early Equidse 

 do to the modern horse. 



2. That in the so-called Spekia zonatus we have a form 

 which even in its most minute anatomical details, as well as 

 in its shell structure, is an unquestionable Naticoid of the 

 Laraellarian type. 



3. That the so-called Tanganyicia rufofilosais closely 

 related to the oceanic Planaxids, and that it is antecedent to a 

 certain section of the heterogeneous Melanoid group, much in 

 the same way that Littorina is antecedent to another. 



4. That the genus Limnotrochus is really compounded 



might, when their anatomy became known, turn out to be marine derivatives. 

 Smith was unfortunate, however, in his forecast of tlie affinities of Typhobia 

 as a Melania, since it is obvious, from the character of the radula of this 

 mollusc alone, that it has no affinity with that group (see my flgs., ' Quart. 

 Journ. Micr. Sci.,' vol. 41, pt. 1, p. 189). Great credit is, however, due to 

 Smith for his shrewd guess at the marine nature of the halolimnic shells 

 with which he was then acquainted, and more especially so because he was not, 

 as it were, frightened out of his better judgment as a naturalist by the existing 

 geological preconceptions respecting the past history of the African interior. 

 The later classification of the Tanganyika shells given by Bourguignat ('Ann. 

 des Sci. Nat.,' t. x, pp. 1 — 267) is quite unintelligible either as to the means 

 by which his endless species are distinguished from each other, or as to their 

 affiliation in his so-called natural groups. Indeed, as an example of the utter 

 confusion and obscuration of the facts which may be produced by the un- 

 restrained application of the conchological method of determining moUuscau 

 affinities when the animals contained in shells are quite unknown, this work is 

 perhaps unrivalled. In M. Fischer's excellent conchological treatise, on the 

 other hand, there will be found a careful estimation in each case of the ))robable 

 affinities of those Tanganyika shells which were known. But each of these is, 

 of necessity, simply drawn from conchological data, and the caution with which 

 the author proceeds in the absence of all morphological information is 

 most marked. In order that the reader may obtain a clear conception 

 of the points in which what may be called the newer classification given in 

 the text of this paper differs from and extends that which could be arrived 

 at by the study of the empty shells, I give here in parallel columns for com- 

 parison a list of the families and genera with which the Halolimnic Gas- 

 teropods are incorporated in M. Fischer's work, and those to which I should 

 myself refer them after a study of the morphology of each. In this list I 



