64 



COELENTEEATA SPONGIAE 



CLASS I 



From.), (Figs. 89, 90). Thick-walled, cylindrical, simple, or branching. Cloaca 



tubiform, extending to the base ; base sometimes covered by dense dermal layer, 



the rest of the exterior finely perforate. A distinct canal-system absent. The 



coarse, anastomosing skeletal fibres composed of closely packed three-rayed and 



one-rayed spicules. Sparse in Devonian (P. constricta, Sandb. sp.) ; common in 



Trias, Jurassic, and Cretaceous. 



Eii*il>]n>in-U<ii Zitt. (Fig. 92). Similar to preceding, but thin-walled, with 



broad cloaca extending to the base, into which conduct radial canals arranged 



in vertical rows. External surface perforate. Upper Jurassic. 



Corynella, Zitt. (Fig. 91). Knob-like, cylindrical, or top-shaped, thick- walled, 



simple, or composite. Cloaca funnel-shaped, shallow, terminating below in 



a series of vertical 

 branching tubes ; ex- 

 halent aperture often 

 surrounded with radi- 

 ally diverging furrows. 

 Ostia conducting into 

 numerously branching 

 radial canals, which 

 unite again in larger 

 excurrent canals, and 

 open into the cloaca. 

 Common in Trias, Jur- 

 assic, and Cretaceous. 

 Usually composite stocks made up of hemi- 



spherical, or short pear-shaped persons, with base enveloped by compact dermal 



layer. Summit dome-shaped, with shallow cloaca surrounded by radial furrows ; 



radial and vertical 



canals terminating 



along sides and basis 



of cloaca. Skeleton 



constituted of short, 



blunt, and bent uni- 



axial, and also of 



three- and four-rayed 



spicules. Triassic and 



Jurassic. 



Holcospongia, Hinde ; 



Jurassic and Creta- 



~ 7 , 



CCOUS. bestromOStella, 



Zitt. 



FIG. 92. 



Rnxil>lionella Bronni, 

 Miinst. sp. Coral-Rag; 

 Nattheiin. Natural size. 



. FIG. 93. 



Oculospongiu, 

 tul)uli/era,Gol<lf. 

 sp. Kreidetuff ; 

 M a e s t r i c h t. 

 Natural size. 



Stellispongia 

 Qnenst. sp. Coral 

 Nattheiin. Natural size. 



Stellispongia, d'Orb. (Fig. 94). 





FIG. 95. 



l^ii'xirtostoma ucutiinargo, Roein. 

 Hils ; Berklingen, Braunschweig. 

 Upper surface, natural size. 



llli/>hi<.1onema Farring<l<>u< //.<( , 

 .Sharps sp. Lower Cretaceous 

 (Aptiaii) ; Farringdon, Berkshire. 

 -/3 natural size. 



Oculospongia (Fig. 93) and Diplostoma, 



Trias to Creta- 



ceous. Synopella, Zitt. ; Cretaceous. 

 From. ; Cretaceous. 



Eiasmostoma^ From. (Fig. 95). Foliate-, ear-, or funnel-shaped. Upper (i.e. 

 inner) surface covered with smooth dermal layer, in which large shallow" oscula 

 are situated ; under surface cribriform. Cretaceous. 



Rhaphidonema, Hinde (Fig. 96). Beaker-, funnel-, or twisted leaf -shaped. 

 Inner or upper surface smooth, with very small oscula or pores. Outer surface 

 rough, cribriform. Canal-system indistinct. Trias, Jurassic, Cretaceous. 



Paehytylodia, Zitt. Funnel-shaped, thick-walled ; base with smooth dermal 



