M. K. A. Zittel on Fossil Calcispongice. 67 



of radial canals remind one of Peronella, and the indication 

 of segment-formation, although but slight, of the two last- 

 mentioned genera. The smooth epitheca, which extends up 

 to the vertex, is characteristic of Himatella. 



The only known species occurs in the Alpine Trias : — 



Tragos milleporatum, Miinst. Beitr. iv. Taf. i. fig. 17. 

 Peronella, Zittel. 



Scyphia, Siphonia, Spongia, auctt. 



Etidea p. p., Hippalimus p. p., D'Orb. 



Siphonoccelia p. p., Pobjccclia p. p., Discoclia p. p., Stenocoslia, From. 



Pareudea p. p., Etal. 



Dendrocoslia, Laube. 



Cceloconia, Dyoconia, Lymnorea, Plioccelia, Siphonoccelia, Lmioccclia , 



Pom. 

 Spongites, Dermispongia, Padicispongia, Querist. 



Simple, or branched by gemmation ; individuals cylin- 

 drical, thick-walled; vertex convex, rarely flat, in the middle 

 with the narrow circular osculum of the tubular stomachal 

 cavity, which, retaining nearly the same diameter, traverses 

 the whole length of the sponge-body to the vicinity of the 

 base. Incurrent canals wanting. Wall of the stomachal 

 cavity and surface porous. Outer surface either naked or 

 coated with a dense concentrically wrinkled epidermis at the 

 base, and sometimes up to the neighbourhood of the vertex. 



The skeleton consists of generally coarse, vermiform, anas- 

 tomosing fibres, which form a confused tissue. In the irre- 

 gular-shaped meshes and interstices of this the water circu- 

 lated, no special canals or ostia being necessary. The pore- 

 like orifices on the surface and on the wall of the central 

 canal are merely gaps in the vermiform tissue. 



In general the skeleton still consists of carbonate of lime ; 

 but in certain localities, especially of the Upper Jura, nearly 

 all the specimens are silicified. In the latter the spicules of 

 which the fibres consist are never preserved. In calcareous 

 skeletons, on the contrary, the microstructure may usually 

 be detected with certainty, although distinctly preserved spi- 

 cules are rarely observed. 



The vermiform fibres appear chiefly to be composed of tri- 

 radiate (perhaps also quadriradiate) spicules, but simple bacil- 

 lar spicules are often associated with these in great numbers. 

 The size and form of the triradiates, and especially the length 

 of the individual, sometimes curved arms, vary considerably 

 in the different species. 



This rich genus, which extends from the Trias into the 

 Upper Cretaceous, may be distinguished easily from the 



5* 



