ORDER IV SILICISPONGIAE —HEXACTINELLIDA 59 
Stauroderma, Zitt. Funnel-shaped or plate-like, with broad and_ shallow 
cloaca, into which the large, round postica of short canals open. Inner and 
outer surfaces provided with dermal layer, in which stellate spicules are em- 
bedded with reduced externally 
and internally directed rays. 
Upper Jurassic. 
Casearia, Quenst. —§ Cylin- 
drical, with numerous annular 
constrictions. Cloaca deep, 
tubiform ; dermal layer re- 
latively thick, and made up 
of cemented stellate spicules. 
Upper Jurassic. C. articulata, 

Goldf. sp. om 
Porospongia, V Orb. (Fig. 77). i . 
Compressed and expanded, Fic. 77. 
more rarely bulbous or cylin- _ Porospongia impressa, Goldf. sp. Upper Jurassic ; Muggendorf, 
Franconia. a, Fragment in natural size; 6, Dermal layer, /} ; 
drical. Superior surface pitted 7 "Sycleton, 12);. 
with large exhalent apertures 
of short, blindly terminating cloacae, and covered over with a dense or finely 
perforate silicious skin, in which cruciform spicules and regular hexactins are 
embedded. Lattice skeleton with cubical meshes ; intersection nodes imper- 
forate. Upper Jurassic. 
Family 4. Ventriculitidae. Toulmin Smith. 
Wall intricately convoluted ; folds radially disposed, generally vertical in direc- 
tion. Radial canals ending blind. Longitudinal furrows developed along folds of 
the wall, and either open, or partially covered - 
over with dermal layer, which is usually a 
formed by thickening of the outer skeletal a ste ail 
layer. Skeletal framework with octahedrally ae 
perforated nodes. Roots consisting of elon- 

= 5 Fie. 79. 
1G. 78. 5 Bind : Ake ‘ 
ae yn ; ~ Ventriculites striatus, Smith. Quadratenkreide ; 
Pachyteichisma Carteri, Zitt. Upper Jurassic; Hohenpolz, Linden, near Hanover. a, Sponge, !/. natural 
Franconia. a, Sponge, 1/2 natural size ; b, Skeleton, 12/,. size ; b, Transverse section, 1/; ; c, Skeleton, 1%/}. 
gated silicious fibres united by transverse bridges and without axial canals. Jurassic 
and Cretaceous. 
Pachyteichisma, Zitt. (Fig. 78). Turbinate or bowl-shaped, with very thick, 
