SCYPHIDIUM. 21 



list) in which the hexaster consists of oxyhexasters and of disc- 

 ohexasters in three varieties differing in size and appearance 

 (macrodiscohexaster, mesodiscohexaster and microdiscohexaster). 

 Now, Scyphidium in the scope given it by me differs from 

 that genus chiefly in the fact that the hexaster occurs in 

 only two varieties, the macrodiscohexaster of Rossella being 

 wanting here. However there can be no doubt of the especially 

 close relationship existing between the two genera. As another 

 very close ally of Scyphidium is certainly to be considered 

 Vitrollula ferlilis Ij., which however lacks not only the macro- 

 discohexaster but also the mesodiscohexaster seen in Eossella, the 

 only discohexaster-form present being apparently the microdisco- 

 hexaster. 



The chief differential characters of the species of Scyphidium 

 may be seen from the following key. 



«. — Dermalia, stauiactins. 



a*. — Pentactinic hypodennalia with smooth, regularly cruciate paratangential s. I^arger 

 discohexaster 80 \j-, and microdiscohexaster 40 ;a in dia. Oxyhexaster, about 100 \>. 



in dia. Sponge with stalks; without prostalia 



'S'. septentrionale Y. K. ScH. (N. of Spitzbergen). 



6'. — Pentactinic hypodermalia with either paratropal or regulary cruciate paratangen- 

 tials, which are either smooth or shagreen-like. Larger discohexaster 90-1Ö0 |J., 

 and microdiscohexaster 24 [i, in dia. Oxyhexaster, 100-122 \i. dia. Sponge witli 

 contracted base ; with long and conspicuous diaetinic ijrostalia, in addition to 



which pentactinic prostalia may occasionally occur 



S^ longispina (Ij.). (Sagami Sea). 



6. — Dermalia, pentactins and stauractins. Pentactinic hypodermalia with smooth regularly 



cruciate paratangentials. Sponge with thick stalk-like base. 



c'.- — Larger discohexaster of 100 ij. dia. leading down to microdiscohexaster of .'!5 {)■ 



dia. Oxyhexaster, 5o-7G \i. \\\ dia. Without prostalia 



>S'. namiyei (IJ-). (SHgami Sea)- 



t/i. — Larger discohexaster of 100 a dia. leading down to microdiscohexaster of 20 i'- 

 dia. Oxyhexaster in two varieties; tlie smaller and thinner-rayed, 80-100 [J. ; and 

 the larger, 120-150 u. in dia. Synapticular fusion among parenchymalia. Prostal- 

 ia? S. sp. (Messier Canal in Chile. Vide F. E. ScJi. '99). 



