104 



ROYAL SOCIETY OF CANADA 



P. tctranema. Suix'rtieial or defensivo spicules very numerous und some- 

 what long and slender, so as to give a lui-sute appearance, and in flat- 

 tened specimens often to obscure the Itody s])icules. Eoot, single, stout, 

 often three inches long, with two to four short, spreading l)ranches at 

 base. These terminal spicules are flattened at the extremities. The 



Fig. 8. — Protosjionqia mononema. Primary, secondary 

 and tertiary spicules, x 5. 



andioring-rod in this species is often nicreased in thickness by a crust or 

 frosting of pyrite, and this would seem to indicate that it had, like the 

 modern Hyahmema, animal matter as well as silica in its composition, or 

 that foreign organic bodies attached themselves to it. 



Nearly as abundant as the preceding form, which it diflers from in 

 the character of the anchoring-rod. each of which may be regarded as a 

 single elongated anchor-shaped spicule, with five rays. The skeleton 

 spicules are also more slender and delicate, and their rays longer, and 

 there is a greater development of protective dermal spines. The osculum 

 is narrow and with many long defensive needles. (Plate I., Fig. 3) 



3. — Protospongia polynema, Dawson. 

 (Figs, it and 10.) 



Fig. \). -Profospomjifi 2)ol!jti<iiia. Portion 

 of base of larj^e specimen. 



A large sponge in great shapeless flattened patches, several inches in 

 diameter, though there are smaller individuals also. Body spicules fine 

 and slender, making a very oj)en mesh. At base numerous simple root 



