656 PALAEONTOLOGY OF ILLINOIS. 



RHOMBOPORA? ASPERULA Ulrich. 



PL LXX. figs. 9 9e. 



Zoarium ramose, growing from an expanded base, attached to 

 foreign bodies. Stems from 1.0 to 1.6 mm. in diameter, branch- 

 ing dichotomously at variable intervals. When in a good state 

 of preservation the surface is very rough or hirsute, the blunt 

 spines or acanthopores being very prominent, and so abundant 

 that the zooecia apertures are obscured by them. Apertures 

 usually suboval, but rather variable in size, shape, and arrange- 

 ment. Measuring in an obliquely transverse direction, about six 

 occur in 1 mm. Interspaces rounded, varying in thickness from 

 one-fourth to three-fourths or more of the diameter of the aper- 

 tures, depending largely upon the maturity of the specimen. 



The irregular arrangement of the zooecia apertures, and the 

 prominence of the spines, distinguish this species from all others 

 of the genus known to me. The first peculiarity is so at var- 

 iance with the ordinary species of the genus that I am inclined 

 to believe that better sections than I have yet been able to 

 prepare will show the species to belong to some other genus, 

 probably Batostomella. 



Position and locality: Keokuk group; Keokuk, Iowa, Nauvoo 

 and Warsaw, 111. 



RHOMBOPORA? SPIRALIS Ulrich. 



PL LXXI. Fig. 5-5d. 



Zoarium a rather robust stem, 1.5 to 2 mm. in diameter, not 

 observed to branch. Zooecia apertures arranged in diagonal 

 spiral series which intersect at an angle of between 70 and 

 80. Measuring along the series there are five in 2 mm. 

 The apertures are subcircular, 0.21 mm. in diameter, and 

 separated by rounded interspaces, bearing a single or double 

 series of contiguous hollow nodes, which are represented by a 

 series of minute pores when the surface of the zoarium is 

 abraded. These pores are quite distinct in thin sections, though 

 not of uniform size, those in the longitudinal interspaces being 

 the largest. Transverse sections are interesting because they 

 show that the zocecia are arranged in a spiral manner about 

 the axis of the branch. This is a verv unusual feature among 

 Palaeozoic Bryozoa. 



