64 COELENTERATA—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. 
Eusiphonela, 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 

ny : cee 
Fic. 93. unite again in larger 
Fic. 92. Oculospongia Fic. 94. c ide sane < 
| poculospongia 1G. 9 excurrent canals, and 
Eusiphonella Bronni, sp. Kreidetuff ; Stellispongia glomerate, Open Into the cloaca. 
Miinst. sp. Coral-Rag ; Maestricht. QnenS s BeUee arts eta in Tri 
Nattheim. Natural size. Natural size. Nattheim. Natural size. Common in Trias, Jur- 
assic, and Cretaceous. 
Stellispongia, VOrb. (Fig. 94). 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. 

Fig. 96. 
Ne r) ye ~ Q5 
Holeospongia, Hinde; Fig. 95. Rhaphidonema Farringdonense, 
Jurassic and  Creta- EKiasmostoma acutimargo, Roem. Sharpe sp. Lower Cretaceous 
2 Hils; Berklingen, Braunschweig. (Aptian); Farringdon, Berkshire. 
ceous. Sestromostella, Upper surface, natural size. 2/3 natural size, 
Zitt.; Trias to Creta- 
ceous. Synopella, Zitt.; Cretaceous. Oculospongia (Fig. 93) and Diplostoma, 
From. ; Cretaceous. 
Elasmostoma, From. (Fig. 95). Foliate-, ear-, or funnel-shaped. Upper (#¢. 
inner) surface covered with smooth dermal layer, in which large shallow oscula 
are situated ; under surface cribriform. Cretaceous. 
?thaphidonema, 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, 
Pachytylodia, Zitt. Funnel-shaped, thick-walled ; base with smooth dermal 
