176 



Fig. 73. Ptihiilicti/n plumen. Nat 

 ural size, anil ]Mirtii>ii of surface en 

 larged (after Hall and Sinipsouj. 



(Fig;. 7-;.) (Pal. X. Y., 



Genus PTILODICTYA. L(ixsdai.e. 



[Ety. : Ptilon, feather; dicti/on, net.] 

 (1839: !Miirchis(m"s Silurian System, p. (JTB.) 



"Zoariiim" (Brvozoimi) '"pointed below, artienlating- 

 into a 8|»i-ea(ling' base; above, a leaf-like ex])ansion, Avliich is 



sometimes lolled at the distal 

 extremity, eelluliferous on both 

 faces, divided by a mesial lamina. 

 Marg-iii withont cells. Apertures 

 circular (jr sulxpiadrate. No in- 

 tercellular tissue, although some 

 s])ecies show minute interaper- 

 tural pits or tubuli on the sur- 

 face of the stipe." (Hall, Pal. 

 N. Y., Vol. VI., pp. xix., XX.) 



Ptilodictya plumea. Hall. 

 Vol. Yl., p. 271, PI. LXI.) 



Distinguishing Characters. — Flattened wedge-sliaped form ; 

 circular or broadly oval apertures; obsolete peristomes; ele- 

 vated, granulose, interapertural space; low convex monti- 

 cules, with somewhat largei- ajtei-tures; striated 

 cylindrical basal ])()rtion. 



Found at " Hambui-g-on-the- Lake. Ei-ie 

 County. X. Y." (Hall): and in the Demissa V)ed, 

 at Section ."), iu Eig'hteen Mile Creek (i-are). 



Genus GLAUCOX()^^0. (Joldfuss. 



[Ety.: Mythological name.] 

 (1826: Petrefacta Geimaniiv, 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 mannei' of growth as the pi-imai'v 

 Fig. 74. oiati- racliis ; celluliferous on one side. Cell a])ertiu'es 



conome carina- • , ... j. i i i "j. !• i 



ta. Enurged,x6 lu two I'auges, otten sej)arated by a longitudmal 



(after Hall and . ., , tt n r> t \t \- a- i \i • , 



Simpson). cariua. (HaJI, Pfu. X. i .. NoJ. \ i.. \). xxiv.) 



