VIÏKOLLULA Ö7 



general that the discohexasters, irrespective of size, have o-o (or 

 occasionally more), slender and faintly rough-surfaced terminals 

 to eacli very short principal. All the terminals so radiate from 

 the ends of principals that a spherical shape is given to the 

 entire spicule. The arched terminal disc is composed of o-S, 

 distinctly developed, recurved prongs. 



VITROLLULA Ij. 



In '98 I included two species under this genus ; but since 

 I now consider that one of them had better be referred to 

 Scyphidium and have described it above as S. namiyei, there 

 remains only V. fertilis to represent the genus. A generic 

 diagnosis may therefore be dispensed with. 



The genus and species is a small-bodied sponge, which would 

 be difficult to distinguish from a Lanuginella or a Leucopsacus 

 without a microscopic examination of the spiculation. This close- 

 ly resembles that of Scyphidium, of Crateromorpha and of Hyalas- 

 cus. It differs from that of the first mentioned genus mainly in 

 that the parenchymalia iuclude hexactins and in that discohexasters 

 occur in a single form which apparently corresponds to the 

 microdiscohexaster. In these respects the agreement with certain 

 Crateromorpha may be said to be almost complete, but the con- 

 spicuous difference with respect to the size and shape of the body 

 may be regarded as sufficient to Avarrant the generic distinction. 

 The difference from Hyalascus consists again in the much small- 

 er size and further in the presence of hexactinic parenchymalia, 

 in the oxyhexasters being pertinently normally developed, &c. 



