BRYOZOA. 659 



R. persimilis has the zooecia apertures arranged in regular 

 diagonally intersecting series (about as in fig. 12b, PI. LXX), 

 the summit of the interspaces granulose when perfect, and the 

 tubes in the axial region straighter and without diaphragms. 

 In the Burlington limestone species R. gractiis, the zooecia are 

 smaller and differently arranged. 



Position and locality: Chester group. Rather abundant at 

 Kaskaskia, 111. Less common at Chester, Illinois, and Sloan's 

 Valley. Ky. 



RHOMPOPORA PERSIMILIS Ulrich. 



PI. LXX, fig. 3. 



Khombopora persimilis Ulrich, 1884. "Am. Pal. BIT." Jour. Gin. Soc. Nat. Hist. Vol. 

 VH, p. 30. 



The figure above cited represents an unusually large example 

 of this species, in a slightly abraded condition. The arrange- 

 ment of the zooecia is as in the typical specimens, only the 

 apertures are a trifle wider, since, measuring transversely, there 

 are only five where they show six. This, I believe, is accounted 

 for by the increased circumference of the larger specimen. Meas- 

 uring diagonally both show eight in 2 mm., and longitudinally 

 nine and ten in 5 mm. 



Position and locality: Chester group. The specimen here fig- 

 ured is from Chester, 111., where more typical examples have 

 also been found in moderate abundance. The species also occurs 

 at other localities in Illinois, and at Sloan's Valley (Tateville), 

 Ken tuck v. 



RHOMBOPORA MINOR Ulrich. 



PI. LXX, fig. 4-4a. 



Zoarium irregularly ramose, branches not rigid, from 0.5 to 

 0.9 mm. in diameter. Zooecia apertures suboval, averaging 0.12 

 mm. in length, situated at the bottom of the deep and illy de- 

 fined areas; arranged, generally, in rapidly ascending but not 

 very regular diagonal series, with about four in 1 mm. Inter- 

 spaces narrowly rounded, never cariuate. carrying, beside a 



