112 j-OYAL SOCIETY OF CANADA 



Genus PAL^OSACCUS Minde. 

 (London Geologicul Magazine, February, 1893.) 



Cylindrical globular or sac-like sponges, with thin walls of rhombic 

 meshes. The strands of the mesh-work consist of fascicles of slender rods, 

 cruciform, and, perhaps, five- rayed spicules ; the interspaces are either 

 open or covered with a thin layer of irregularly disjjosed rods and cruci- 

 form spicules. No anchoring spicules have been found in immediate 

 connection with the sponge, but there are with it on the same surfaces 

 elongated anchoring-siMcules with ornamented spiral ridges which may 

 belong to it.' 



From Cyathophycus, "Walcott, which appears to be nearest allied, this 

 genus is distinguished by the rhombic character and large size of the 

 mesh-work ; the generally similar structure both of the longitudinal and 

 transverse strands of the mesh, and the greater development of rod-like 

 (Spicules. The same features likewise differentiate it from Plectodeima, 

 Hinde, and Phoniiosella, Hinde. 



10. — Pal.«:osaccus J)/;wsoni, Ilinde. 

 (Figs. 22 and 23. PI. III., Fig. 9, PI. IV.) 



Fig. 22.— Spiral anchorinp;-rod8, 

 distal ends enlarged. 



Fig. 23.— Portion of anchoring- 

 rods, enlarged 



Sponge of large size, apparently cylindrical in its complete form ; 

 the part preserved consists of a flattened portion of the wall-surface more 

 than a foot in diameter ; both the upper and the basal portions of the 

 sponge are wanting. The rhombic meshes of the wall vary from 14 to 

 20 mm. in width, the average width is nearly 17 mm. The strands of 

 the mesh mostly consist of very slender rod-like threads apparently 

 simple, which are loosely arranged, in strands of five or more, generally 

 parallel with each other. At the angles of the mesh there are, very 

 frequently, if not in all cases, stouter crucifornii, or perhaps five-rayed 



^ TraAofor, ancient ; oukko^, coaree cloth, sack, strainer. 



m 



