66 



Canadian Record of Science, 



glabella of Triarthrus on the back, which proves its geolo- 

 gical horizon. It has two specimens of Gyathophycus close 

 together, nearly perfect at their bases and broken off at the 

 height of about three inches. They are perfectly flattened 

 and pyritized, which is also the conditioa of other fossils in 

 these shales, with the exception of the graptolites, which 

 seem to have resisted this kind of change. 



The genus Gyathophycus was originally described by "Wal- 

 cott from specimens obtained at Trenton, Oneida Co., New 

 York.^ He regarded it as an alga, whence the tej'mination 



^ Trans. Albany Instit-, 1879. 

 "phycus," but subsequently, in the American Journal of 

 Science, 1881, corrected this error, and referred it to the 

 sponges. Hall (35th Eegents' Eeport) properly places it 

 with the reticulate sponges included in his family Dictyo- 

 spongidae, but does not add much to Walcott's original 

 description, to which the present specimens permit some 

 additions to be made. 



The specimens are perfectly flattened, but show distinct 

 indications of the two sides of the originally conical form. 

 The wall of the skeleton has evidently been thin and com- 

 posed of slender bundles, each of a few long simple spicules, 

 and increasing both by bifurcation and the introduction of 

 new bundles, so as to preserve nearly the same distances in 

 the wider parts of the cone. They are very regular in the 

 lower part, where there are about nine principal, with 

 some intei-mediate secondary bundles in a centimetre, but 

 become more irregular toward the top. This may, how- 

 ever, be an effect of decay and crushing. At the base these 

 bundles become thicker, and in a specimen from the origi- 

 nal New York locality, kindly lent to me by Mr. Ami, I 

 have observed that they become expanded and converted 

 into somewhat short clavate root spicules. This is, how- 

 ever, not appai'ent in Mr. Miller's specimens, which may 

 have been broken off" at the surface of the mud. 



The vertical bundles are crossed at right angles by hori- 

 zontal spicules much less regularly arranged, but dividing 

 tho surface into rectangular meshes. These are slightly 



t 



