124 PROCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



a hypobranchial gland, it stands apart from those other members of the 

 Volutidae whose anatomy is at present known. The three characters 

 mentioned may, from what we know of prosobranch anatomy, be 

 reasonably regarded as primitive features, and when we remember 

 that the genus Volutilithes was originally founded to embrace a 

 number of fossil forms common in the Cretaceous, Eocene, and 

 Oligocene beds, it becomes extremely probable, if the conchological 

 identification be correct, that the form would retain a more primitive 

 organization than the more recently developed genera, such as Koluta, 

 Melo, etc. Such being the case, I am inclined to regard Volutilithes 

 as the living form which stands nearest to the ancestors of the 

 Volutidae, and one which, while it had acquired or inherited certain 

 of the characteristic features of the Volutidae, nevertheless retained 

 a number of characters belonging to its less specialized rhachiglossate 

 ancestors. 



One difficulty stands in the way of this conclusion, viz. the nervous 

 system of Melo Neptuni, in which we find the supra -intestinal ganglion 

 separated by a long interspace from the right pleural. With regard 

 to this point I cannot help thinking that possibly the condition seen 

 in Melo is not, after all, a primitive character, since this form is in 

 other respects a highly specialized Volute, and since also in other 

 groups of Prosobranchs the relative degree of proximity between these 

 two ganglia seems to vary, so much so that I believe it is possible 

 for this separation to be at times a new secondary condition arising 

 from a concentrated one, and not a direct inheritance of the primary 

 architaenioglossate condition. 



From the above remarks it will be gathered that our knowledge 

 of the anatomy of the Volutidae and of the whole rhachiglossate 

 group is still very meagre, and we must at present regard the classi- 

 fication of these forms as purely provisional. It is extremely probable 

 that we are at present incorporating in the Volutidae several forms 

 derived from distinct stocks ; in other words, this is not a natural 

 family, and in all probability Volutolyria, at least, will have to be 

 separated from the other members of the Volutidae when we know 

 more of its anatomj^. Still, one would think that more use might be 

 made of the radulae by systematists than is at present done, and one 

 has only to look at our textbooks to see what divergent forms are 

 incorporated, not merely in the same family, but in the same genus ; 

 thus, in the genus Mitra forms exhibiting five totally distinct types of 

 radula are included. 



1 have not attempted to define the family Volutidae anatomically, 

 because I consider that we need a great deal more information before 

 such a definition can be possible ; but I think that the presence of 

 two pairs of pre-neural salivary glands, one tubular and one grape- 

 shaped, an oesophageal caecum, the concentrated nervous system, as 

 described above, together with a radula with a tricuspid central 

 tooth ( ? sometimes unicuspid), will be found to be characteristic of 

 all Volutes. 



The importance of a knowledge of the anatomy of any form is well 

 exemplified by such a form as Neptuneopsis, and will be still more 



