ORDER III 



SILICISl'OXCJTAE LITHISTIDA 



61 



iMuiran ( Fiii. Hi'//). Body spherical, with perforate periphery, 

 ..f attachment wanting. All canals radiate from the centre outward. 

 Skeletal elements composed of three simple rays heset with prickly tubercles, 

 and a n-dii.-.-d l.iit ton-like fourth arm. All spicules regularly disposal in rows 

 parallel with radial canals. Silurian ; North America. 



Sub-Order C. ANOMOCLADINA. Zittel. 

 (Didymmorin a, Rauflf. ) 



dements composed of short, smooth rays ivith spherically inflated ends 

 i/ in- a ff three, four, or more simple or digitate branches; the latter are united 

 with processes of adjacent rays ; axial canals simple. Dermal spicules 

 ,-,/. slmji,, I nmnaxons. Upper Jurassic and Recent. 



<'i/liiiiln>i>/i i/ma, Zitt. (Fig. 63). Body cylindrical, thick-walled, attached; 

 cloaca wide and tube-like, receiving numerous radial canals, and extending 



FIG. 63. 



'/ '/'I* i/iiin iiiilli-iiitrntii, (H)lilt'. sj>. I'lipcr Malm; Horhst riiss. A, Two individuals, I/., natural siz-. 

 /.'. Skt-li-toii magnified 30 diaiuctrrs. < '. Di-tachcd skeleUil element of Cylindrophyma, 60/ x (after Kauft'). 



down as far as the base. External surface perforated by fine ostia. Common 

 in I'ppcr Jurassic. 2'b! cs 



Mi-/i>iir/l<i, Xitt. Skeleton apple-shaped or hemispherical, with broad base, 

 or provided with very short peduncle ; base covered with wrinkled silicious 

 skin. Cloaca deep, funnel-shaped. Coarser canals arched, parallel with peri- 

 phery ; finer incurrent canals radially directed. Upper Jurassic. M. radiata, 

 ^Hi-list, sp. 



Sub-Order D. MEaAMORINA. Zittel. 



( //// abdomorina, Rauff. ) 



Usually large-sized, elongated, smooth, lent, loosely interl<>d-in<t, Irregularly branch- 

 i. ;/. or only terminally forked skeletal elements with simple axial canals ; interspersed 

 among which small, radicifoi-m, numerously branching elements (rhizomorins) are 

 occasionally present. Dermal spicules uniaxial or grapnel -shaped. Ordovician. 

 Silurian, Carboniferous, Jurassic, Cretaceous, and Recent. 



