43 



IV. CONCLUSION. 



Recapitulating the contents of the preceding pages, we come to the conclusion that the 

 Siboga-Expedition has been able to secure 65 specimens of Solenogastres, belonging to 8 genera 

 (4 new genera) and to 12 species (all of them new), viz; 



Proneomenia Weberi 11 specimens Depth 22 — 1633 M. 



Proneomenia longa 2 specimens Depth 1158 M. 



Dinomenia Hubrechti 2 specimens Depth 73 M. and pelagic 



Dinomenia verrucosa 11 specimens Depth 32 — 112 M. 



Proparamenia bivalens 2 specimens Depth 82 M. 



Rhopalomenia indica 28 specimens Depth 18 — 560 M. 



Rhopalomenia debilis 1 specimen Depth 75 — 94 M. 



Hemimenia intermedia 2 specimens Depth 69 — 75 M. 



Cyclomenia holosericea 1 specimen Depth 918 M. 



Dondersia annulata 1 specimen Depth 55 M. 



Chaetoderma Lovéni 3 specimens Depth 13 10 M. 



Chaetoderma Wiréni 1 specimen Depth 1570 M. 

 The different depths do not present any peculiarities on corriparison with those of the 

 known species; the greatest depth of Proneomenia Weberi (1633 M.) however, exceeds that 

 of the species of Proneomenia already described. This depth has only been surpassed by that of 

 Chaetoderma nitidulum (1250 fathoms, Simroth 7, pag. 208). Pelseneer (12) mentions as the 

 greatest depth 3088 M. This is based on an error. At St. 202 a depth of 3088 M. was indeed 

 met with ; but in the fishing the trawl was made no use of; only the horizontal cylinder was 

 used, the specimen of Dinomenia Hubrechti, caught in this case, being consequently found 

 living free at the surface, and apparently leading a pelagic life, which has hitherto not been 

 noticed among Solenogastres. 



In various respects our knowledge of the Solenogastres has been extended by the 

 Indian forms. 



There is good reason for dividing the Neomeniidae into 2 groups : 



A) Those with a thick cuticle, papillae, and long pointed spicula in many layers one above 

 the other. 



B) Those with a thin cuticle. without papillae, with flat, imbricated spicula. 



Both groups must remain distinctly separated, only Paramenia might be called intermediate, 

 though it is more closely related to group B than to group A. I ara of Pruvot's opinion in 

 considering the type of group B the most primitive one. 



Taking the radula however as the principal point of comparison, we notice 3 groups : 



C) Forms with polystichous radula. 



D) Forms with distichous radula. 



E) Forms without a radula. All these forms may be considered as having sprung from forms 

 with radulas and should be considered specialized forms. 



