502 M. K. A. Zittel on Fossil Hexactinellida. 



? EOSPONGIA, Billings. 

 Geol. Surv. of Canada, Paloeozoic Fossils, vol. i. p. 10. 



Family 2. Euretidse. 



Pkotospongia, Salter. 

 Quart. Joui-n. Geol. See. 1864, vol. xx. p. 238, pi. xiii. fig. 12*. 



Calathium, Billings. 



Geol. Surv. of Canada, Palaeozic Fossils, vol. i. 1865, pp. 208-211, 

 .335-338, 358. 



? Teach YUM, Billings. 

 Ibid. p. 211. 



Aech^ocyathus, Billings. 

 Ibid. pp. .3-5, 354. 



? Steganodictyum, M'Coy. 

 Palaeozoic Fossils of the Cambridge Museum, pi. ii. A. figs. 1-4. 



Teemadictyon, Zitt. 



Cup-shaped, plate-like, cylindrical. Central cavity wide. 

 Wall on both surfaces with rather large rhomboidal or oval 

 ostia standing in alternating series. Eadial canals blind. 

 Root nodose. Latticed skeleton of the wall and root con- 

 sisting of large but unequal and irregularly formed meshes, the 

 arms of the coalescent sexradiates being frequently thickened 

 or lamellarly dilated. Crossing-nodes solid. Surface of tlie 

 wall on both sides covered by an extremely delicate meshed 

 net of coalescent sexrediates, which also veils the ostia. Boot 

 without ostia and canals. 



Sc7/j}7iia reticulata, Goldf., Taf. vi. 1. 

 {S. 2)olyommata, Goldf.) 

 Spongites ohliquatuSj Quenst. Jura, Taf. 81. 97. 



Ceaticulaeia, Zitt. 



Sponge-body simple or branched. Both surfaces with 

 numerous roundish or oval ostia, which stand in vertical and 

 horizontal series and cross each other at right angles ; some- 

 times the ostia of one surface also lie in longitudinal furrows. 



* ?Amphispvngia, Salt. (Mem. Geol. Surv. Explanation of Edinb. 

 Sheet, &c., pi. ii. fig. 3), possibly belongs here, but perhaps to the 

 Lyssakina. 



