MARYLAND GEOLOGICAL SURVEY 22p 



ARTHROPORA CLEAVELANDI (James) 

 Plate LIII, Figs. 14, 15 



Ptilodictya cleavelandi James, 1881, Paleontologist, No. 5, p. 38. 

 Arthropora cleavelandi Bassler, 1906, Proc. U. S. Nat. Mus., vol. xxx, p. xiv, 

 pi. 3, figs. 13-16; pi. 4, fig. 6. 



Description. Ptilodictya cleavelandi James, as shown by the type, is 

 founded upon segments of a rather well-marked species of Arthropora 

 occurring abundantly throughout the various subdivisions of the Eden 

 shale. The species is characterized by slender, generally nonbifurcating 

 segments (in consequence of which the complete zoarium must have con- 

 sisted of comparatively only a few rigid branches) and by the numerous 

 and small lateral branchlets springing out at nearly right angles from the 

 main stem. The segments are usually found separated, specimens retain- 

 ing more than a sequence of two or three being extremely rare. Ir 

 length they vary but little from the average of 7 mm. The basal seg- 

 ment is bifurcated and drawn out acuminately below. 



The zocecial apertures are as usual in this genus, elliptical, surrounded 

 by a delicate peristome. The interspaces have one or more thread-like 

 ridges, variously disposed and with a row of minute papillae. 



Occurrence. MARTINSBURG SHALE (Eden division). Pennsylvania 

 and Maryland. Jordans Knob, one and one-half miles northeast of Fort 

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

 McConnellsburg, in Pennsylvania, and the western slopes of Fairview and 

 Rickard Mountains, Washington County, Maryland, are localities where 

 the species may be found. 



A characteristic and abundant species of the Eden shale at Cincinnati, 

 Ohio, and vicinity. 



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



