50 COELENTERATA—SPONGIAE CLASS I 
or only distally covered with tuberculous knobs, and with digitate extremities. 
Dermal spicules in the form of six-lobed disks provided with a short shaft, and 
minute, multifid tetraclons. Upper Cretaceous. 
Sub-Order B. EUTAXICLADINA. Rauf. 
Skeleton composed of four-rayed spicules with three equally developed simple or 
hifurcate rays which terminate distally in root-like fibres; and one foreshortened, 
inflated fourth ray (ennomolcon). Aaial canals probably in all of the rays. Skeletal 


ox 
FE) 1 (> 

Fic. 61. 
Astylospongia praemorsa, Goldf. sp. In erratic from Mecklenburg. a, Sponge, partially cut into, natural size ; 
b, Skeleton, 12/;; c, Portion of same highly magnified. 
elements invariably arranged in either parallel or alternating rows, and united by 
zygosis into a network with triangular or irregular meshes ; spicular nodes greatly 
inflated. 
Nearly all the genera are Silurian ; a few (Jastosia, Lecanella) occur in the 
Upper Jurassic. 
Astylospongia, Roem. (Figs. 61, 62a). Spherical, with shallow depression on 
the summit ; base evenly rounded, unattached ; probably fastened by means of 
anchoring fibres. Large-sized canals directed 
b parallel to periphery in the outer portion of the 
body, vertical in central portions; besides these 
are numerous fine radial canals which termin- 
ate in pores all over the periphery. Skeletal 
elements with four smooth elongated rays, one ~ 
Fic. 62, or all of which branch dichotomously just 
a, Detached skeletal element of Astylo- above the junction with the shorter arm. 
of Himdia, 8: (etter Raney cae flement’ Syicular nodes thickened into large knots. 
Ordovician of the Russian Baltic Sea Pro- 
vinces, and Silurian of Sweden and North America (notably in Tennessee), 
usually chalcedonised. Also in erratics in the Diluvium of Northern Germany. 
Caryospongia, Carpospongia, Rauff. Ordovician and Silurian ; Europe. 
Palaeomanon, Roem. (Astylomanon, Rauft). Like Astylospongia, but bowl- 
shaped, with shallower and wider cloacal depression. Entire surface covered 
with pores. Silurian; North America. P. cratera, Roem. 
Caryomanon, Carpomanon, Ranft. Silurian; North America. 

