BRYOZOA. 655 



mm. The arrangement of the apertures is not very regular. 

 The longitudinal series are as a rule more noticeable than the 

 diagonal rows. The latter intersect each other at an angle of 

 90 or more. Measuring longitudinally, twelve to fourteen aper- 

 tures occur in 5 mm.; diagonally 6.5 to 7.5 in 2 mm. 



The transverse marking of the branches, and the less regular 

 arrangement of the zooecia apertures separate this species from 

 R. vnrmns. Xone of the other are very closely related. 



Position and locality: Keokuk group, Plymouth, Xauvoo 

 and Warsaw. 111. 



RHOMBOPORA ATTENUAT * Ulrich. 



PL LXX, flg. 7. 



Zoarium a slender stem, from 0.7 to 1 mm. in diameter; not 

 observed to branch. Zooecia apertures arranged very regularly 

 in longitudinal and diagonal series, which intersect each other 

 at an angle of about 45. Interspaces rather thin, acutely ridge- 

 shaped, bearing upon the summit a single series of very small 

 and closely set nodes. The node at the angle is commonly larger 

 than the others. Areas rather narrow, regularly long-hexagonal, 

 truncated at the ends, sloping rapidly down into the oval aper- 

 ture, whose long diameter is about 0.15 mm., the shorter 0.10 

 mm. Longitudinally, there are sixteen apertures in 5 mm.; 

 diagonally five in 1 mm. 



This species is closely allied to R. wortbeni from the Lower 

 Carboniferous (? Keokuk) deposits of Kentucky. The cells of 

 that species are a little larger and scarcely so regular in their 

 arrangement, and the stems stronger, being from 1.2 to 1.8 

 mm. in diameter. The R. exigua of the Burlington limestone, is 

 even more slender, has smaller apertures, rounded interspaces, 

 larger granules, and the ends of the areas pointed instead of 

 truncate. The last fact causes the diagonal rows of apertures 

 to ascend more rapidly in their spiral course around the stems. 



Position and locality: Not "uncommon in the upper layers of 

 the Keokuk group at Warsaw, 111. 



