ORDER IV SILICISPONGIAE—HEXACTINELLIDA aid 

and merely indicated by cavities. The more important fossil forms are divided 
into the following families. 
Family 1. Craticularidae. Rautl. (Euretidae, p. p., Zittel non Schulze.) 
Cup-shaped, cylindrical, branching, or flattened sponges. Spreular nodes solid. 
External surface without distinct dermal layer, but protected by a thickening of the 
outer skeletal layer, and 
occasionally covered 
with a delicate web of * 
cemented spicules. 
Cunals simple, blindly 
terminating wm the 
skeleton. Jurassic. 
Tremadictyon, 
Zitt. (Fig. 73). Cup-, 
plate-shaped, or 
cylindrical, with wide 
cloaca. Canal-open- 
ings on both sides 
in alternating rows. 
Base nodular; ex- 
terior veiled over aaa 
with delicate net- Tremadictyon reticulatum, Goldf. sp. Upper Jurassic ; Streitberg, Franconia. 
work ofamalgamated a, Sponge, 2/5 natural size ; b, Enlarged portion of outer surface withoutjdermal 
S layer ; c, Portion with well-preserved dermal layer, #/) 3 d, Skeleton, 12/). = 

hexactins, extending 
even across canal pores. Skeletal framework with more or less irregular 
cubical meshes. Very common in 
Upper Jurassic. 
Craticularia, Zitt. (Fig. 74). Funnel- 
shaped, cylindrical, or flattened ; simple, 
or branching. Canal-openings on both 
surfaces either round or elliptical, and 
regularly distributed in vertical and 
ooo ° 02 oa horizontal rows. Canals short, ending 
i Mi , . . 
fea g00 blind. Jurassic, Cretaceous, and 
Miocene. 
Sporadopyle, Zitt. Cup- to funnel- 
shaped or conical, occasionally branch- 
ing. Canal-openings on outer surface 
Fic. 74. irregularly distributed, or arranged in 
Craticularia poradora, Mnstr. sp. Upper Jurassic; quincunx; on cloacal surface in vertical 
D iMieed akaloton, 3) 5 o°Thickencd formaliayer, TOWS. Upper Jurassic. 8. obliqua, 
Goldf. sp. 
Sphenaulax, Zitt., Verrucocoelia, Etall, ete. Jurassic. 

Family 2. Coscinoporidae. Zittel. 
Calycoid, beaker-like, lobate, branching, or stellately convoluted sponges, with thin 
walls perforated on both sides by numerous canal-openings arranged in alternating 
