875 



Ehin. 



(X 60) globate spicules, got by dissolving the rock in acid; f. 

 6 (X 200; one mounted in glycerine, showing minute points on 

 its surface which are the ends of the siliceous fibres of which 

 the sponge is composed; f. 7, another globate spinule magni- 

 fied 660 diameters; f. 8 (X 200) another mounted in Canada 

 bal sam showing fibres; f. 9 (X 200) another showing the effect 

 of corrosion on its surface, whilst the interior has been replaced 

 by banded chalcedony; f. 10 is one which shows an unaltered 

 surface and a similarly replaced centre. These figures are here 

 given because the discovery of miscropic globules, as well as 

 of visible needles, in fossil sponge structures, showing also their 

 dissolution, explains the extensive beds of chert in several 

 formations in Pennsylvania, especially the Chert beds of F/, 

 described by Claypole in his Report F 2 on Perry Go. VI— 

 Note. For Ugure see Appendix. 

 Rhinopora fondosa, Hall and Whitfield. Pal. N. Y. Vol. 



2, 1852, page 48. 



1875, page 1 12, plate 

 5, fig. 8, natural size 

 a fragment, showing 

 the arrangement of 

 spots (macule) and 

 _ ._ ,. grooves on the sur- 



FixLOhio . Vol, lU Piatt V, ^^^''''''''''''^ ^^^^ . gg 2^ 'en- 



largement of one spot, showingthe clustering of the larger 

 pores. This bryozoon grew over surfaces in thin broad irreg- 

 ular expanses, cellulose only on one face of it. The slightly 

 elevated spots seem to center at the fork of a groove. Much 

 like R. verrucosa^ Hall, from Flamboro Head, Canada West, 

 from the same Clinton limestone as this at Dayton, Ohio; but 

 the grooves are in that species raised lines. V a. 



Rhizodus angustus, Newberry, Proc. Acad. Nat. Sci. Phila. 

 Vol. 8, 1857, Pal. Ohio, Vol. 1873, page 342, plate 39, fig. 6, wa^ 

 ^^y-^Z^?^^, partof jaw with teeth, of one of the Linton, Ohio, Coal 

 measure fishes ; teeth showing a tendency of barbing at the point, 

 as do those oi Lepidosteus ; folded base of tooth, as usual, gone, 

 leaving only the solid point, abput an inch long, entire tooth hav 

 ing been two inches. This is an unusual occurrence of teeth in 

 the jaw; isolated teeth being frequently found, and with them 



