652 PALEONTOLOGY OF ILLINOIS. 



not sharply margined, the summit of the interspace being nar- 

 rowly rounded and occupied by a row of closely set small gran- 

 ules. Often two rows of granules prevail for a short distance. 



The granulose interspaces and more slender stems separate 

 this species from R. gracilis with which it is associated. E. at- 

 tenuata, from the Keokuk group, has larger and more regu- 

 larly arranged zooecia apertures, and sharply margined areas. 



Position and locality: Burlington group, Burlington, Iowa. 



EHOMBOPORA ANGUSTATA Ulrich. 



PL LXX, figs. 6, 6a. 



Zoarium an exceedingly slender cylindrical stem, 0.4 to 0.5 

 mm. in diameter; not observed to branch, but probably doing 

 so at long intervals. Zooecia apertures arranged in rather ir- 

 regular diagonally intersecting series. Sloping area large, elon- 

 gate elliptical or lozenge-shaped, averaging 0.5 mm. long by 

 0.2 mm. wide. Summit of interspaces sharp, crowded with a 

 closely arranged row of small nodes, which form flexuous lon- 

 gitudinal Knes. Apertures 0.17 mm. long and one-half as wide, 

 about five in 3 mm. longitudinally. It requires between five 

 and six zooecia to form one oblique volution about the stem. 



The small size of the stems, the comparatively large zooecia, 

 and the elongate sloping area about their apertures, constitute 

 the distinguishing features of this species. 



Position and locality: Keokuk group. "Rather rare at King's 

 Mountain, Ky. 



RHOMBOPORA INCRASSATA Ulrich. 



PL LXX, figs. 12-12d. 



Zoarium a rather robust straight stem, from 1.2 to 1.8 mm. 

 in diameter, occasionally sending off branches of the same size 

 at about a right angle. Apertures arranged transversely, longi- 

 tudinally, and in diagonally intersecting series which ascend the 

 stem spirally, making an angle of about 40 with the axis of 

 the stem. Interspaces very thick, ridge-shaped, bearing upon 

 the summit a single or sometimes double series of closely set 



