200 J. E. S. MOORE. 



It will be seen from all this that the Typhobias and other 

 Tanganyika Gastropods possess crystalline styles and cseca 

 which have identically the same relations^ and are structures 

 which are undoubtedly homologous with the similar forma- 

 tions present in numerous Lamellibranchiata, and in a few 

 other Gastropods as well. Now the practical importance of 

 these facts to the present inquiry is this, that the particular 

 Gastropods in which as yet the caecum has been indubitably 

 recorded, are Strombus, Pterocera, Rostellaria, Murex 

 vertagus, Trochus turritus, the two species of Typhobia 

 at present known, and the so-called Tanganyika Litho- 

 glyphus. It may also possibly be present in Bythinia. 

 Once more, then, the Typhobias in the characters of their 

 stomachs and their related caeca are structurally near to those 

 marine families with which by the character of their nerves 

 and radulse they were seen to be akin. In the possession of 

 a style and its sac they further exhibit anatomical features 

 possessed by the Lamellibranchs on the one hand, and by the 

 connecting link between the Lamellibranchs and the Proso- 

 branchs, the diotocardiate Trochi, on the other. 



The gills in Typhobia are very similar to those in 

 Strom bus and Pterocera, and the osphradium resembles 

 completely the same structure in all those Strombi which I 

 have examined. The heart, as will be seen from reference to 

 page 190, possesses the characters which are exhibited by 

 nearly all the Tsenioglossa. 



The siphon possessed by the Typhobias is a structure of 

 doubtful value from a classificatory point of view, and even in 

 its narrower application it is by no means to be trusted, as both 

 Bouvier and Haller have already shown. An interesting 

 example of the impossibility of separating the holostomous 

 from the siphonostomous Prosobranchs has come before 

 me during the present investigation, for while examining 

 one of the Melanias which the authorities of the British 

 Museum generously placed at my disposal for compa- 

 rison, I found in one, the exact species of which was doubtful, 

 and which had been collected by Mr. Cuming in the Philippine 



