238 M. K. A. Zittcl on Fossil LWiistidLe. 



With central stomachal cavity or scattered oscula. Stomachal 

 cavity sometimes replaced by vertical tubes. Sponge-body 

 composed of more or less distinctly qnadriradiate or irregularly 

 ramified skeletal elements, furnished at the ends of the branches 

 or throughout their whole length with nodular or root-like pro- 

 cesses, intimately interlocked, but not soldered together; and 

 sometimes of these and of surface-spicules of quadiiaxial or uni- 

 axial type. The surface-spicules either forked anchors with a 

 long shaft directed inwards, or short-stemmed anchors with 

 curved and sometimes nodular or branched flukes, or, lastly, 

 uniaxial spicules of variable form and size. Besides these, in 

 the sarcode, minute flesh-spicules of uniaxial type. 



Family 1. Rhizomorina. 



Skeletal corpuscles irregularly branched, beset with shorter 

 or longer, simple or composite root-like processes or nodular 

 excrescences, with a simple or branched central canal. Skele- 

 tal elements grouped together into confused fibres, or loosely 

 interlocked with each other. Surface-structures frequently 

 like those of the rest of the skeleton, but uniaxial spicules and 

 forked anchors are also present. 



A. Skeletal corpuscles moderately ramified, with a short, 

 simple canal in tlie main stem ; loosely interlocked with each 

 other (see PI. VIII. fig. 6). 



a. Sponge-body thick-walled, top-shaped, nodular, or basin- 

 shaped, with vertical radial fissures, which are frequently 

 furcate towards the outside, and into which run fine radial 

 canals standing serially one above the other. 



Cnemidiastrum, Zitt. (Jura). Top-shaped, nodular or basin-shaped, with 



small round caual-ostia ou the radial fissures. 

 Coi-aUidimn, Zitt. (Jura). Top-shaped ; surface coated with epidermis 



up to the upper margin. 



b. Sponge-body basin-shaped, top-shaped, or laminiform. 

 Radial canal-system very fine, indistinctly developed ; in the 

 centre sometimes vertical canals. 



Hyalotragosj Zitt. (Jura). Basin-shaped or top-shaped ; oscula on the 

 inner surface ; vertical canals present. 



Pyrgochonia, Zitt. (Jura). Basin-shaped; elevated oscula on both sides; 

 vertical canals in the centre. 



Discostroma, Zitt. (.Tura). Disciform ; upper surface convex, frizzled, 

 •with a central cavity ; lower surface with smooth epidermis. 



JEpistotnella, Zitt. (Jura). Laminiform ; upper surface with elevated 

 oscula ; lower surface porous. 



Leiodorella, Zitt. (Jura). Laminiform, cylindrical, nodular; both sur- 

 faces with margined oscula ; between them smooth epidermis. 



P/oft/c/tonifi, Zitt. (Jura). I^aminiform ; both surfaces with line pores. 



