17G 



I ii. ;:', Ptilodictya plumen Nat- 

 oral si/.i'. and portion of Burface ftn- 

 larged i after Hall and Simpson;. 



73. 



(Pal. X. V., 



Genus PTILODICTYA. Lonsdale. 



[Ki'v. : Ptilon, feather; dictyon, net.] 

 (1839: Murchison's Silurian System, p. 676.) 



"Zoarium" (Bryozoum) "pointed below, articulating 

 into a spreading base; above, ;i leaf-like expansion, which is 



sometimes lobed at the distal 

 extremity, celluliferous on both 

 faces, divided by a mesial lamina. 

 Margin without cells. Apertures 

 circular or subquadrate. No in- 

 tercellular tissue although some 

 species show minute interaper- 

 tural pits or tubuli on the sur- 

 fa,ce of the stipe." (Hall. Pal. 

 \". V.. Vol. VI.. pp. xix.. xx.) 



Ptilodictya plumea. Hall. ( Fi; 

 Vol. VI.. p. 271. PL LXI.) 



Distinguishing Characters.— Flattened wedge-shaped form ; 

 circular or broadly oval apertures; obsolete peristomes ; ele- 

 vated, granulose, interapertural space: low convex monti- 

 cules, with somewhat larger apertures; striated 

 cylindrical basal portion. 



Found at " Hamburg -on -the -Lake, Erie 

 County, X. V.*' (Hall): and in the Demissa bed, 

 ;it Section 5, in Eighteen Mile ('reek (rare). 



Genus GLAUCONOME. Goldfuss. 



[Ety. : Mythological name. ] 

 dS-,'6: Petrefacta Germanic, Vol. I., p. 100.) 



" Zoarium consisting of a main stem orrachis, 



from which proceed simple lateral branches at 



regular intervals, and occasionally branches hav- 



ing the same manner of growth as the primary 



„„ pachis; celluliferous on one side, (ell apertures 



s 



Fie. 74. Gl 

 , onome i "> nm 



ta Eniwged, xfl m t wo ranges, oiten separated bya longitudinal 



er Hall aud .. TT .. , . .. .. .. . frT . 



Simpson). carina. ( Hall. \ K ,\\. .\. l .. vol. V I., p. xxiv. ) 



