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and omitted to place this new group after Septaria, which latter I consider to belong to the 

 family Neritidae. My new family has been attacked by Dr. Simroth and by Prof. Thiele; the 

 latter who had the kindness to send me his paper (Über die Anatomie von Hydrocena cattar- 

 oensis Pfr., in Abh. der Senckenb. Naturf. Gesellschaft in Frankf. a/M., Band 32, p. 351 — 358) 

 acknowledges the genus, but is inclined to let it remain in the family Neritidae. This is one 

 of the questions of appreciation of characters, not easy to be solved in a decisive manner, I 

 think such a considerable difference might be sufficiënt, at all events the shape of the teeth, 

 especially of that replacing the "Schirmplatte", does not agree with the family-characters as 

 they were limited till recently. As to Dr. Simroth, he accuses me of having divided the group 

 into two families "on conchological characters", as I see in his paper which I detected on 

 p. 27 of the Proceedings of the Mal. Society of Londen, Vol. IX, 1910. I must reply that 

 this accusation is quite wrong; if Dr. Simroth had carefully read that part of my work, he 

 would have perceived that it is only in the first place on anatomical characters, that I erected 

 the family, for as far as I am aware, the radula is still generally considered as belonging to 

 the anatomical side of a mollusk. If one ought to consider the radula or the genital organs 

 to be of more importance I will not decide, but I have had so much satisfaction of my 

 researches of the radula, that I cannot consider it as of little value. The union of Nerita and 

 Septaria in one genus as according to Simroth's paper has been accomplished by Prof. Bourne 

 "in the first place upon the genital organs" will, I hope, not convince many malacologists, for 

 though the splitting up of families and genera may have gone too far in many instances, I 

 think science will not be promoted by mixing groups of such a diversified appearance of shell 

 and operculum, even if closely allied in some other respects. 



