BRYOZOA. 661 



RHOMBOPORA NICKLESI Ulrich. 



PI. LXX. fig. l-lc. 



Zoarium consisting of small, dichotomously branching stems, 

 averaging 0.6 mm. in diameter, but varying from 0.4 to 0.9 

 mm. Interspaces rather narrow, sloping rapidly down on each 

 side into the oval apertures, which have an average length of 

 about 0.17 mm. The summit of the interspaces is narrowly 

 rounded or sub-angular, and mostly smooth, excepting at the 

 angles of junction, where it rises into a more or less conspicu- 

 ous node. On each side of the summit, and marking the top 

 of the suboval or lozenge-shaped area, there is an exceedingly 

 minute series of closely arranged granules, which are too small 

 to be shown in the illustrations. Zooecia apertures ranged in 

 rather regular diagonal lines, intersecting at an angle of 

 about 65: with four in 1 mm. Sometimes the zooecia aper- 

 tures are narrower on one side of the stem than on the other. 



The external appearance of this species is very much like that 

 of Rhabdomeson rhombiferum Phillips, from the Carboniferous 

 shales of Scotland, but numerous thin sections show that there 

 is no axial tube, and that the minute characters agree in all 

 respects with Rhombopora. R. lepidodendroides Meek, is larger, 

 and has a single or double row of distinct granules on the sum- 

 mit of the interspaces between the large spines at the angles. 

 R. persimilis of the Chester limestone has wider interspaces and 

 differs internally. 



The specific name is given in honor of Mr. J. M. Xickles, of 

 Sparta, Illinois, to whom we are indebted for the discovery of 

 this and many other new Bryozoa from the Lower Carbonifer- 

 ous and Coal Measure deposits of Illinois. 



Position and locality: Lower Coal Measures, Sparta, 111. 



ACANTHOCLEMA Hall, 1887. 



(Pal. N. Y. Vol. VI, p. XV.) 

 (For generic diagnosis see page 402). 



I propose, provisionally, to adopt this genus, for species dif- 

 fering from typical Rhombopora, in having the zooecia apertures 

 arranged between longitudinal ridges. Some of the species 



