112 



ROYAL SOCIETY OF CANADA 



riENUS PAL.EOSACCUS Hindc. 

 (London Geologicul Magazine, February. 1803.) 



Cylintlrifal glolmlar or aac-like sponges, with thin walls of rhombic 

 moslR's. The strands of the mesh-work consist of fascicles of slender rods, 

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

 open or covered with a thin layer of irregularly di8i)osed rods and cruci- 

 foiT.i spicules. No anchoring spicules have been found in immediate 

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

 elongated anchoring-spicules with ornamented spiral ridges which may 

 belong to it.' 



From Ci/dthojjhi/cns, Walcott. which appears to be nearest allied, this 

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

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

 transverse strands of the mesh. an(i the greater development of rod-like 

 spicules. The same features likewise differentiate it from Pkctodenna^ 

 Hinde, and Phormoaella, Hinde, 



10. — Pal^osaccus Dawsoni, Ilinde. 

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



Fig. 22.— Spiral anchorinK-rods, 

 distal ends enlarged. 



Fig. 23.— Portion of anchoring- 

 rods, enlarged 



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

 the part ])reserved consists of a flattened portion of the wall-surface more 

 than a foot in diameter ; both the upper and the basal poi'tions of the 

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

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

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

 simple, which are loosely an-anged. in strands of five or more, generally 

 jtai-allel with each other. At the angles of the mesh there are. very 

 frc(|uenlly. if not in all cases, stouter cruciform, or pcrlaips tive-rayed 



' namwc^ ancient ; namntr, coarse cloth, sack, strainer. 



