ORDER III 



SILICISPONGIAE— LITHISTIDA 



57 



Suborder 4. MEGAMORINA Zittel. 



(Rhabdomorina RaufF.) 



Usually large-sized, elongated, smooth, bmt, loosely interlocking, irregularhj 

 hranching, or only terminally forked skeletal Clements with simple axial canals ; 

 interspersed among which small, radiciform, numerously hranching Clements 

 {rhizomorins) are occasionally present. Dermal spicules uniaxial or grapnel-shapcd. 

 Ordovician, Silurian, Carboniferous, Jurassic, Cretaceous and Recent. 



Saccospongia Rauff. Silurian. Megalithista Zittel. Upper Jurassic ; 

 Nattheim. 



Dory derma Zittel (Fig. 59). Sponge-body cylindrical, simple or branching, 

 pyriform or compressed, with a number of larger canals running parallel 

 with the body 

 axis, and numer- 

 ous smaller radial 

 canals. Skeletal 

 Clements large, 

 bent and divided 

 into two or more 

 simple branches. 

 Dermal spicules 

 in the form of 

 three - fluked an- 

 chors. Upper 

 Cretaceous ; Nor- 

 thern Germany, 

 England and Fig. 59. 



France AcCOrd- Doryderma dichotoma (Roemer). Upper Cretaceous. a, Sponge, natural size ; b, 

 TT- J Dermal layer, 2/^; c, Bündle of skeletal elements, lo/j ; d, Skeletal element and 



ing to xlinde, also several dermal spicules with furcate, anchor-shaped head-rays, 30/^. 



Carboniferous. 



Gartcrclla Zittel ; Astcroderma Schrammen. Cretaceous. 



Isorhaphinia Zittel. Sub - cylindrical, pedunculate, with wide cloaca 

 reaching nearly to the base. Skeletal elements large, slightly bent, rod- 

 shaped, inflated at the ends, rarely dichotomously branching. They are 

 associated in bundles, and so interlocked at their extremities as to form 

 an open meshwork. Cretaceous. /. texta (Roemer). 



Suborder 5. RHIZOMORINA Zittel. 



Skeletal elements small, composed of four or of three principal rays, or simple and 

 irregulär, with numcrous projecting spines or tubercles ; axial canal simple or branching. 

 Dermal spicules monaxons, tetraxons or similar to those of the skeleton. Chiefly 

 Jurassic, Cretaceous and Recent. 



Nipterella Hinde. Cambrian. 



Cnemidiastrum Zittel {Cnemidium, p. p. Goldf.) (Fig. 60). Turbinate or 

 bowl-shaped, with deep cloaca. Walls thick, p^rforated by numerous radial 

 canals disposed in tiers one over another, thus forming vertical fissures which 

 often divide toward the exterior. Skeletal elements irregularly branching, 

 entirely beset with blunt spiny processes. Abundant in the Upper Jurassic 



