400 PALEONTOLOGY OF ILLINOIS. 



Family ARTHROSTYLID.E Ulrich. 



Zoaria articulated, ramose, consisting of numerous sub-cylindri- 

 cal segments, or, if dichotomously divided, of continuous branches, 

 which articulate with a slightly expanded attached base. Zo- 

 cecia sub-tubular, more or less oblique, radially arranged around 

 a central axis, opening on all sides of the segments; more 

 rarely, one side is non-celluliferous and striated longitudinally. 



ARTHROSTYLUS. n. gen.* Zoaria dichotomously divided, com- 

 posed of numerous slender equal segments, joined to each other 

 by terminal articulation ; poriferous on one side only ; opposite 

 side longitudinally striated. Zooecia arranged in three or more 

 rows, between carinse. 



Type: Arthronema tenue Ulrich ("Amer. Pal. Bry.") Range, 

 Trenton and Cincinnati. 



ARTHROCLEMA Billings. Zoarium articulated, composed of 

 numerous sub-cylindrial segments arranged in a pinnate man- 

 ner, those forming the central stem the largest. Each of the 

 primary segments with one or two sockets on each side for 

 articulation with the smaller secondary segments; these again 

 in like manner articulate with still more slender tertiary seg- 

 ments. Celluliferous on all sides. Zooecia somewhat oblique, 

 with nearly direct oval apertures, arranged between elevated car- 

 inae. A diaphragm may intersect the tube at about the middle 

 of its length. 



Type: A. pulchellum Billings. Range, Trenton and Cincinnati. 



SCEPTROPORA 11. gen. Segments club-shaped, the lower half 

 striated, non-celluliferous, the extremity bulbous ; upper half ex- 

 panded, the center of the top with a large socket. Zooecia tub- 

 ular, arranged between vertical lines; apertures sub-ovate. 



about 1.5 mm. ; width of branches about 0.5 mm. Zooecial tubes arranged bilaterally 

 two on each side of a vertical lamina, not observed at the surface. Celluliferous face 

 not seen. Zooecia (as shown by tangential sections) tubular, with broadly oval aper- 

 tures, their longer diameter 0.12 mm., about four in one mm. Walls thin within, rapidly 

 thickening toward the aperture. One or two diaphragms in most of the tubes. 



This interesting species I obtained from the Peter Bedpath Museum of Montreal, 

 Canada, through the kindness of Sir Wm. Dawson. The specimens were collected by 

 Mr. T. Curry, at Montreal, from the Trenton limestone. 



* This name is proposed instead of Arthronema which was pre-occupied by sch- 

 scholtz. 



