45 



but it is not improbable however that in the future the genus Proneomenia will be divided into 

 smaller genera. As Proneomenia Weberi and longa show the principal characteristics of the 

 genus Proneomenia (polystichous radula, structure of the integument, 2 salivary glands, no 

 gills), a division of this genus should as yet not be recommended. 



What has been noticed in Proneomenia, holds good for Rhopalomenia. Whilst in Rhopalo- 

 menia aglaopheniae and Kisigi the loss of the radula points towards their origin from speciejs of 

 Proneomenia, it is much more probable that Rhopalomenia indica and debilis are related to a 

 form like Dinomenia. The numerous receptacula seminis of Rhopalomenia indica point towards 

 some relation with Dinomenia verrucosa, just as the rudimentary radula-sac of Rhopalomenia debilis 

 points to a certain relation with Dinomenia, which has a distichous radula. However a relation 

 between Rhopalomenia indica and Proneomenia thulensis is also very well possible. The absence 

 of a radula in Pronomenia and Dinomenia may give rise to forms closely resembling each other 

 both of them with a thick cuticle, pointed spicula in many layers, 2 long salivary glands, no radula. 



Proparamenia and Paramenia differ considerably in the structure of the integument. A 

 transition-form between the two is not known, but the possibility of such a form is proved by 

 Cyclomenia, which has a thick cuticle and needle-shaped spicula, but is without papillae. For 

 the rest Cyclomenia and Dinomenia are related to Paramenia, and show that the integument 

 may develop in the direction of Proneomenia, whilst the radula remains distichous. 



As a consequence of these facts, the relation between the known Neomeniidae may be 

 established as follows : 



Dinomenia 



Cyclomenia- 



Pararrhopalia 



Pruvotia 



Strophomenia 



Notomenia(?) 



Rhopalomenia indica 

 and debilis 



Proneomenia thulensis 



Rhopalomenia aglaopheniae and Eisigi 



Proneomenia 



Proneomenia Weberi Proneomenia vagans Kow. & M 



and longa 



Proparamenia 



Macellomenia 

 Paramenia 



Amphimenia 



Stylomenia 



Hemimenia-Neomenia 



— Dondersia' 



Myzomenia 



Nematomenia 



Echinomenia lsmenia Lepidomenia. 



