[DAWSON] FOSSIL SPONGES AND OTHER ORGANIC REMAINS 



6. — Protospongia cyathiformis, Dawson. 

 (Figs. 15 and 10. PI. II., Figs. 7 and 8.) 



107 



Fig. 15. — Protospongia cyathi- 

 formis. Restored. 



Fig. IQ.— Protospongia cyathiformis. Primary, 

 secondary and tertiary cruciform spicules, x 5. 



General form inverted conical. When mature about 3 cm. wide at 

 top and 5 cm. long, without the anchoring-spicules, which are sometimes 

 veiy long. Top truncate as if with a wide osculum, with defensive 

 spicules on its margin. Primary spicules cruciform, with long rays, in 

 some 2 to 3 mm. in length, placed diagonally, loosely attached or free 

 but forming large rhombic meshes ; secondarj^ and tertiary spicules 

 numerous and delicate, Avith slender arms. Eoot spicules simple, some- 

 times very long, five or moi-e visible in the most perfect specimens, and 

 passing up to the middle of the body. Indications of many interior 

 minute flesh spicules, often constituting a p3n'itized mass, obscuring the 

 meshes. 



The oblique character of the transverse spicules deserves notice, but 

 tliis may be the result of compression, though I think it more likely that 

 it is an original feature. 



This species is well characterized by its form, and by its multitudes 

 of very minute cruciforui spicules. These, and the fact of the spono-e 

 being often represented by a dense, pyritous mas.s, indicate a thicker and 

 more fleshy body-wall than in some other species. 



