294 



of the mostly quadiangularly rounded sections of tlie zoa^cial cavities. Just as 

 the kenozoo^cia mentioned seen from the surface (fig. 2 a) are of very different 

 form and size, the same is the case with their transverse sections, and the inner 

 cavity in some of considerable size is in others almost slit-like, hi two of them 

 (one on the left and one on the right side) there is only a distinct cavity in the 

 one half, whilst in the other the two walls lie close up against one anollier, and 

 this enables us to readily understand why these kenozoa'cia in many species, e. g. 

 in Ret. Beanianu and Ret. phoenicea, have no inner cavity even in the youngest 

 |)arts of the colony. On the kenozocx-cia arranged in layers we can distinguish 

 between three kinds of walls, terminal separating walls which separate the keno- 

 zoa'cia at different heights, lateral walls which separate the kenozoci-cia at the 

 same height and interjacent walls which separate the kenozocccia in different 

 layers. Whilst the last are provided with pore-canals, the two others are |)rovided 

 with uniporous rosette plates (figs. 2 d and 2 e), which according to the extent of 

 the chambers may sometimes be placed in a zigzag row, sometimes in a single row. 



That we have here actually to do with layers which arise the one outside 

 of the other, is specially distinct in those cases where for example a Spirorhis 

 is fixed on a Retepnru colony, as the tube of the worm then becomes covered by 

 layers which grow up over it from the surface of the colony. This is seen for 

 example on PI. XXIII, fig. 3 a, which represents a section, obtained by grinding, 

 through a colony of Ret. celliilosa from Oran. We see here a Spirorbis tube cov- 

 ered by an expansion, which on the one side is two-layered and on the other 

 single, whilst on each side of the tube there is an elongated, triangular cavity, 

 which separates the covering layer from that on which the tube rests. On PI. X, 

 fig. 2 c is shown a part of a colony of Ret. medilerranca, which is much younger 

 than the fragment represented in fig. 2 b, but here also the frontal surface of Ibe 

 zott'cia is covered by kenozocecia. Fig. 3 b shows a section, obtained by grinding, 

 through the terminal j)art of a branch of Ret. Wdllichidiui and (he kenozotrcia 

 here also are provided with a distinct cavity. 



Time has not permitted me to enter further into the classification of this 

 family, and I have been obliged to restrict myself partly to describe a single 

 incrusting sjiecies, partly to mention a number of earlier described incrusling s[)e- 

 cies, which must be referred to this family. These are for example, Schizotlicca 

 fissa Busk, Schiz. dii'i.sd Norman, Rhijnchozoon^ bi.ipinosiini Johnsf., Rluinch. lonijiro- 

 stre Hincks, Rhi/in-li. pro fund urn Mac (lill., Rliiincli. rrrniildliim Waters, 'Miicronclld 

 tubiilosa Hincks, 'Schizoporellu' arnmld Hincks, Schiz. <^ lucidd Hincks, 'Scliiz.^ 

 scintillans Hincks etc. 



' .\s to the name lilujnchozoon see 2.'>, p. 125 and 38 b, Index. 



