ORDER III 



SILICISPONGIAE— LITHISTIDA 



57 



Rauff. Silurian. Megalithista Zittel. Upper Jurassic 



Spoiige-body cylindrical, simple or branching, 

 a number of larger canals running parallel 



b 



Suborder 4. MEGAMORINA Zittel. 



{Rhabdomorina Rauff. ) 



Usually large-sized, elongated, smooth, bent, loosely interlocking, irregularly 

 branching, or only terminally forked skeletal elements with simple axial canals ; 

 interspersed among tvhich small, radiciform, numerously branching elements 

 {rhizomorins) are occasionally jiresent. Dermal spicules uniaxial or grapnel-shaped. 

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



Saccospongia 

 Nattheim. 



Doryderma Zittel (Fig. 59). 

 pyriform or compressed, with 

 with the body 

 axis, and numer- 

 ous smaller radial 

 canals. Skeletal 

 elements 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 

 France. Accord- 

 ing to Hinde, also 

 Carboniferous. 



Carterella Zittel; Asteroderma 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). 



Fig. 59. 



Doryderma dlchotoma (Roemer). Upper Cretaceous, a, Sponge, natural size ; 6, 

 Dermal layer, 2/^ ; c. Bundle of skeletal elements, lo/j ; rf, Skeletal element and 

 several dermal spicules with furcate, anchor-shaped head-rays, ■^o/i. 



Suborder 5. RHIZOMORINA Zittel. 



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

 irregular, with numerous pjrojecting 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, perforated 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 



