BRYOZOA. 389 



dinal series between slightly elevated, straight or flexuous 

 ridges, carrying a^ crowded row of small blunt spines. Space 

 immediately surrounding apertures sloping up to summits of 

 ridges. 



Type: S. fenestrata Hall. Range, Chazy to Cincinnati, and 

 perhaps also in Lower Helderberg. 



EURYDICTYA n. gen. Zoaria forming broad, simple or irregu- 

 larly divided, bifoliate expansions, without non-poriferous parallel 

 margins. Surface with more or less conspicuous, small, solid 

 maculae or monticules. Zocecial structure very much as in 

 Stictopora, the differences being of small importance and due to 

 zoarial habit. 



Type: E. montifera Ulr. Range, Trenton to Cincinnati. 



DICRANOPORA Ulrich. Zoaria jointed; segments ligulate, rarely 

 simple, usually divided dichotomously at the upper end. Each 

 extremity somewhat thickened and solid. Minute structure and 

 arrangement of zocecia apertures as in Stictopora. 



Type: D. internodia Miller & Dyer. Range, Trenton to Cin- 

 cinnati. 



GONIOTRYPA Ulrich. Like Dicranopora in all respects save 

 that there is a prominent median ridge on each of the two faces 

 of the double-leaved segments. 



Type: G. bilateralis Ulrich. Cincinnati group. 



EUSPILOPORA n. gen. Zoaria consisting of small, flattened, 

 irregularly divided branches. Zooecia apertures subcircular or 

 elliptical, arranged in four or more rows over the central por- 

 tion of the branches between slightly elevated longitudinal 

 ridges, bearing numerous, small nodes. At brief intervals, occur- 

 ing alternately on each side of the branch, there are several 

 short rows of apertures directed obliquely upward and outward 

 from the central rows, extending nearly to the sharp margins. 

 Between these lateral rows the margin of the frond is more or 

 less indented, but a wide depressed non-poriferous space remains. 

 This is covered with exceedingly fine granulose striae. Thin sec- 

 tions show that between the ends of the zooecia there is a verti- 

 cal series of shallow lenticular vesicles, separated from each 

 other by a thick layer of tissue. All the remaining interspaces 

 are traversed vertically by exceedingly numerous minute tubuli. 



