456 Mr. J. E. S. Moore. Zoological Evidence for the 



trunk, the Typhobias undoubtedly approximate to the Solaridas and 

 possibly to the Scalarids. In fact, the structural tout ensemble of the 

 Typhobias leaves little room for question that these gasteropods must 

 be regarded as forms closely similar to a Pteroceras with a non- 

 specialised foot. 



What is true of the Typhobias is also true of the allied genus 

 Bathanalia, except that this form is in some respects more primi- 

 tive, and is certainly less specialised in its shell. The so-called 

 Litkoglyphus zonatus, L. neritinoides, and L. rufqfilosus are seen at 

 once, when anatomically examined, to have been perhaps even more 

 completely misplaced than the Typhobias. In the characters of their 

 radulae and alimentary canals they approximate to the Planaxidce* 

 while in the possession of an anterior stomachic ccecum and style, they 

 show undoubted affinity to some members of the Strombidse. In the 

 character of their nervous system they are undoubtedly akin to the 

 marine Zygoneurous Gerithia on the one hand and the longi-commis- 

 surate Struthiolariidce on the other. But the most remarkable ana- 

 tomical feature which these forms possess is the existence in the 

 female of an enormous epidermal invagination of the body wall 

 beneath the eye (fig. 3), into which the embryos descend from the 

 female genital aperture along a deep groove, and I have now 

 complete evidence for regarding this groove, which is present in 

 both sexes as truly homologous with the similar genital grooves 

 possessed by the Opisthobranchs. The affinities of the new genera 

 Bythoceras, Paramelania, and Nassopsis, are much more difficult to 

 determine, but there is no doubt that in the curious condition of 

 their nerves and in the general features of their anatomy they are 

 extremely primitive. The whole nervous system of these forms, in 

 the forwardly elongated character of the pedal ganglia and in the 

 relation and characters of the cerebral and pleural ganglia and their 

 connectives, actually approximate to that of a Cyclophorus. In 

 other respects it resembles that of Triton. 



Lastly, the one entire Limnotrochus which I possess seems to be 

 nearly akin to the Paramelanian group, but the anatomy of this 

 form will require more fully working out by sections than has yet 

 been done. 



Thus, although I am not yet able to give a complete statement of 

 the character of all the halolimnic molluscs known, enough anato- 

 mical work has now been done for this preliminary communication 

 to indicate clearly what will be the entire result of the investigation. 

 It has been seen that the theory of the marine origin of the 



* It is remarkable that representatives of this family abound in the Indian Ocean 

 and on the East African coast, the so-called Litlioglyphus of Tanganyika affording 

 one among many instances of similarity between the molluscan fauna of Tanganyika 

 and that of the Indian Ocean. 



