[DAWSON] FOSSIL SPONGES AND OTHER ORGANIC REMAINS 

 ♦i. — Protohpdncha cyatiukobmis, I)aw.son. 

 (Figs. 15 and 16. PI. II., Figs. 7 and S.) 



107 



¥\Q. \b.—Protoapongia cyaihi- Fig. IQ.—Protoapongin ci/nfhifoniiis. Primary, 

 formia. Restored. secondary and tertiary cruciform spicules, x 5. 



General form inverted conical. Wlion mature aitout 3 cm. wide at 

 top and 5 em. long, without the anehoring-spicules, which arc sometimes 

 very long. Top truncate as it' 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. l()Osely attached or free, 

 hut forming large rhorahic meshes ; secondary and tertiary spicules 

 numerous and delicate, with slender arms. Root spicules simple, some- 

 times very long, five or more visible in the most perfect specimens, and 

 passing uj) to the middle of the body. Indicati<tns of many interior 

 minute flesh spicules, often constituting a pyritized mass, obscuring tiie 

 meshes. 



The oblique character of the transvei-se spicules deserves notice, but 

 this may be the result of compression, though I think it more likely tliat 

 it is an original feature. 



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

 of very minute ci'uciform spicules. These and the fact of the sponge 

 being often represented l)y a dense, pyritous mass, indicate a thicker and 

 more fleshy body-wall than in some other species. 



