ORDER III 



SILICISPONGIAE— LITHISTIDA 



53 



are very scarce in the Upper Jurassic (Protetraclis), but abundant in the 

 Cretaceous, Tertiary and Recent periods. 



A'ulocopium Oswald (Fig. 48). Hemispherical or bowl-shaped with short 

 peduncle ; inferior surface covered with a dense, wrinkled, siliceous skin. 



Fig. 49. 



Callopegma acaule Zitt. Senonian ; Ahlten, Hanover ; a, Specimen in •*/4 natural size ; h, Skeleton magnified 

 ^o/i ; c, Portion of periphery, ^/j ; d, Same magnified 40/i, and showing anchors with furcate head-rays. 



Cloaca central ; sponge body with numerous arched canals parallel to contour 

 of periphery, and with finer radial canals leading from exterior to cloaca. 

 Skeleton composed of irregular smooth-rayed tetraclons with root-like branch- 

 ing extremities, disposed in rows parallel to the radial canals. Occurs (usually 

 replaced by calcite) in the Ordovician of the Russian Baltic Sea Provinces, 



B 





Fig. 60. 



Phymatella tuherosa (Queiistedt). Quadratenlvreide, 

 ('Upper Senonian) ; Linden, near Hanover, a, Sponge, 

 1/2 natural size ; b, Outer surface, i/i ! ''i Slceletal element, 

 sw/i ; d, Spicules from stalk portion, 50/i. 



Fig. 51. 



Siphonia tulipa Zitt. Greensand ; Blackdown. 

 A, Longitudinal section, natural size. JS, Sponge 

 with jieduncle and root, 1/2 natural, size (after 

 Sowerby). 



Ordovician of Illinois, and Silurian of Gotland. Also in erratic blocks on the 

 plains of Northern Germany, usually chalcedonised. 



Archaeoscyphia Hinde. Cambrian. 



Callopegma Zittel (Fig. 49). Bowl- or funnel-shaped, short-stemmed, thick- 

 walled. External surface perforated by smaller, internal by larger canal-openings 



