BRYOZOA. 637 



DlPLOPORA BIFTJRCATA Ulrich. 

 PI. LXIL fie. ia-12a. 



Zoarium very small, consisting of slender sub-cylindrical 

 dichotomizing branches, about 0.3 mm. in diameter, bifurcating 

 at intervals of from 1 to 3 mm. Obverse side with two ranges 

 of small, zooecia apertures, situated along the margin to which 

 their rather prominent peristonies give a slightly wavy outline. 

 Apertures circular, about 0.08 mm. in diameter, twice their dia- 

 meter apart, with twelve in 3 mm. Between the ranges of aper- 

 tures the surface is rather narrowly rounded but not carinate, 

 and occasionally exhibits a small tubercle. Reverse of branches 

 finely striated. 



It is not improbable that this species has closer affininities with 

 such species of Thamniscus as T. furcillatus, which it resembles 

 in the dichotomization of its branches; but, in the present state 

 of our knowledge, the two ranges of zooecia seem to demand 

 recognition, and I have accordingly placed the species here. 



Position and locality: Chester group, Chester, Illinois. 



DlPLOPORA BISERIALIS Ulrich. 



PI. Lxn, fig. n-iic. 



Zoarium consisting of very slender, sub-cylindrical, straight 

 or slightly curved stems, nearly 0.3 mm. wide and somewhat 

 less in thickness, which throw off, at variable but long intervals 

 precisely similar lateral branches. Margins wavy, due to the 

 projection of the zooecia apertures. Reverse of branches finely 

 striated, evenly rounded. Obverse, with two ranges of alterna- 

 ting zooecia. Apertures subcircular, marginal, opening obliquely 

 outward, with elevated peristome, about 0.1 mm. in diameter, 

 once and a half to twice their diameter apart, with twenty in 

 5 mm. Surface between the ranges of apertures subangular, 

 and marked with faint, intermittent, longitudinal striip. 



The Scotch D. warginalis Y. & Y., to which this species is 

 closely allied, has a thin tuberculated central keel, and usually 

 another on each side of it. The reverse is also granulo-striate. 



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



