[DAWSON] FOSSIL SPONGES AND OTHER ORGANIC REMAINS 



105 



spicules, sliort, tmd, in some eases, expanded at their extremities. Young 

 individuals seem to have been o-lobular and probably sessile, while large 

 individuals had a flat base; but the general form is gi'eatly obscured by 

 erusiiing, especially in the larger specimens. 



Fig. \Q.—Protospongia ijolynema. Priniaiy, secondary 

 and tertiary spicules, x 5. 



4. — Protospongia delicatula, Dawson. 

 (Figs. 11 and 12.) 



Globular or oblong in form, 1 to 4 cm. in diameter. Body spicules 

 cruciform, regular, forming a very dense mesh, about 1 mm. or less in the 

 opening. Osculum probably wide. Defensive spicules very short and 

 close. Several short anchoring-rods. Some indications of a double row 

 of 8i:)icules in the body-wall. The density of the spicular body-wall 

 causes it often to be encrusted and obscured by pyrites. 



tt 



7t3 



#p 



--H- 



Fig. 11. — Protospongia delicatula. (a) Re- 

 stored. <6) Portion of base enlarged. 



Fig. 12.— Primary, secondary and 

 tertiary spicules, x 5. 



Rauff, in his monograph on fossil sponges, identifies this with Wal- 

 cott's Cyathophyctis {Teganiuni) subsphœricus of the TJtica shale, but com- 

 parison with specimens kindly furnished by Dr. Walcott shows that there 



