222 SYSTEMATIC PALEONTOLOGY 



the upper part (Eden) of the Martinsburg shale at Jordans Knob, one 

 and one-half miles northeast of Fort Loudon, Pennsylvania, and west 

 slope of Eickard Mountain, Washington County, Maryland. 



Collections. Maryland Geological Survey, IT. S. National Museum. 



Family HALLOPORIDAE 

 Genus HALLOPORA Bassler 



HALLOPOKA ONEALLI SIGILLAKIOIDES (Nicholson) 



' Plate LIII, Fig. 10 



Chaetetes sigillarioides Nicholson, 1875, Pal. Ohio, vol. ii, p. 203, pi. xxii, 



figs. 9, 9a. 

 Callopora sigillarioides Nickles, 1905, Kentucky Geol. Surv., Bull, v, p. 50, 



pi. ii, figs. 10, 11. 

 Callopora onealli sigillaroides Bassler, 1906, Proc. U. S. Nat. Mus., vol. xxx, 



pi. vi, figs. 3, 4. 



Description. Zoarium ramose, consisting of narrow, dichotomously 

 dividing branches from 2 to 4 mm. in diameter. Surface of branches 

 usually smooth, although occasionally the clusters of larger cells 

 (maculae) are slightly elevated. Apertures of zocecia oval, about six in 

 2 mm. measuring along the length of the branch, and eight in the same 

 space transversely with their longer diameter in the direction of the 

 branch. Mesopores numerous. Diaphragms few in the axial region of 

 the tubes, but rather numerous in the mature zone. In the mesopores 

 the diaphragms are closely spaced throughout their length. 



Occurrence. MARTINSBURG SHALE (Eden division). Very abundant 

 and characteristic of the Eden shale in the Ohio Valley. Upper part 

 (Eden) of Martinsburg shale at Jordans Knob, one and one-half miles 

 northeast of Fort Loudon ; Cowan's Gap, five miles northeast of McCon- 

 nellsburg, and Tuscarora Mountain, two and one-half miles southeast of 

 McConnellsburg, Pennsylvania. The corresponding horizon in Maryland 

 on Eickard Mountain, Washington County, also furnishes specimens. In 

 all of the eastern localities the species occurs as molds in the sandy 

 matrix, but the preservation is so good that gutta percha squeezes readily 

 show all of the specific characters of the surface. 



Collections. : Maryland Geological Survey, U. S. National Museum. 



