BRYOZOA. 611 



ranges throughout. The best specimen seen is slightly abraded. 

 yet shows faint evidences of granulose striations on the inter- 

 spaces. 



This species, though having the branches united by dissepi- 

 ments whenever they approach each other closely enough, is 

 nevertheless a true species of Thamniscus. The fact that dissepi- 

 ments are also occasionally present in T. dubius, the type of 

 the genus, invalidates all objection to them in other species 

 having the really essential characters of the genus. Compared 

 with T. diraricans, the present species will be found much 

 smaller, the branches more frequently bifurcated, and the zocecia 

 apertures differently arranged. A more nearly related species 

 occurs in the Keokuk group at King's Mountain, Ky. It differs 

 mainly in having stronger branches. 



Position and locality: The typical form is from the Chester 

 group at Sloan's Yalley, Ky., and has also been noticed on 

 slabs from Chester, 111. The variety is from the Lower Coal 

 Measures at Seville, 111. 



THAMMSCUS OCTONARIUS Ulrich. 



PL LXH, Fig. 7-7b. 



Zoarium a small flabellate frond, somewhat higher than -wide, 

 produced by frequent bilateral dichotomization of a zigzag 

 primary branch. The bifurcations take place at such short in- 

 tervals that the spaces which separated the branches are usually 

 of less width than the branches. The angles between the bifur- 

 cating branches are rounded, while the separating ranges of 

 zooecia form acute angles, the intervals being occupied by sub- 

 triangular or wedge-shaped, concave, solid spaces. Obverse face 

 of branches moderately convex, 1.1 to 1.3 mm. wide. Zocecia 

 ranges increasing rapidly in number from three or four to seven 

 or eight between the bifurcations. Apertures circular, about 

 0.07 mm. in diameter, arranged in longitudinal series between 

 obscure raised lines, fifteen or sixteen in 5 mm., and in more or 

 less regular diagonal series. Peristome gradually rising about 

 the aperture, incomplete at its lower margin, spreading again 

 and gradually becoming obsolete below the aperture so as to 



