i86 



Cincinnati Society of Natural History 



small papillae. Nonporiferous margins granulose, obsolete above 

 the first bifurcation. 



The dwarfish appearance of this species distinguishes it from 

 R. nic/io/soni, Ulr. That species has much wider branches bifurca- 

 ting at very long intervals. The growth is like in R. minima, but the 

 two species are quite different in other respects, the differences in 

 the size of the zocecia apertures and in the markings of the inter- 

 spaces being especially striking. 



Position and locality: From the lower beds of the Trenton 

 Shales, associated with Stictoporella frondifera and Packydictya 

 fo/irfia, at Minneapolis, Minn. 



PACHYD1CTYA PUMILA, tl. Sp. 



Fig. 11 —Pachydlctya pumila, n. sp. a. three specimens of the natural size. b. a 

 small specimen preserving the base, natural size, and x9. In this specimen the sur- 

 face is well preserved and all the zocecia] apertures open, c and d. two fragments, 

 natural size, and x9, with many of the apertures closed by a granulose secondary 

 deposit. 



Zoarium bifoliate, small; branches from r.o to 1.5 mm. wide, 



bifurcating at frequent intervals. Zocecia in from four to six 



longitudinal rows, with about seven in 2 mm. Apertures elliptical, 



averaging about 0.15 mm in length, and 0.1 mm. in width, 



enclosed by a very thin peristome. Interspaces slightly depressed 



or flat, and, like the moderate non-celluliferous margins, filled with 



small papillae. It happens frequently that these papillae extend 



over large patches of the surface where the zocecial apertures 



have been closed by a thin deposit of calcareous material. In 



very young examples, or at the distal extremities of the branches 



