﻿ULRICH-BASSLER] revision of paleozoic BRYOZOA -I 



unreasonable to doubt the propriety of drawing a specific distinction 

 between them. When the new species was first collected, we believed 

 it would turn out to be a species of Mesotrypa, and possibly the same 

 as the form described on a succeeding page as Mesotrypa angnlaris. 

 Thin sections, however, at once proved the error ol this view and at 

 the same time supplied ample internal differences to distinguish it 

 from all species of the latter genus. 



Occurrence. — Usually very abundant in the lower part of the Her- 

 mitage formation ( Sa fiord's Orthis bed) of the Ordovician section 

 in middle Tennessee, especially at localities in the vicinity of Colum- 

 bia and northward to Nashville. The figured specimens are from an 

 exposure about 4 miles north of Columbia. 



Cat. \os. 43,175-43,177, l\ S. X. M. 



Genus Homotrypella Ulrich 



We have nothing to offer that affects the standing- of this genus, 

 except to say that its usefulness in classification has been confirmed 

 over and over again in the course of our recent studies. Although 

 we have other equally distinct species in our collections that have 

 never been described, the value of the one about to be described as 

 a list fossil, and its desired use in stratigraphic work now under way, 

 have led us to give it a place in this paper. Similar reasons have 

 determined the matter of immediate publication for all other new 

 species that do not modify generic definition. 



HOMOTRYPELLA NODOSA new species 

 (Plate VII, 1-3) 



This very abundant Lorraine species is readily recognized by the 

 closely set, sharp or rounded, often elongate monticules studding the 

 surface of its subcylindrical, frequently dividing branches. These 

 are often 1 1 mm. in diameter, though usually 1 or 2 mm. less. 

 Under a pocket lens the entire surface appears minutely spinulose, 

 and when closely examined it will be observed that the spines are set 

 about the mouths of the zocecia in such a manner that the latter are 

 given a beautiful petaloid or rayed appearance. The zocecia are 

 smaller than those of other species of the genus, 10 occurring in 2 

 mm. The acanthopores also are small but very numerous, as many 

 as 12 occurring around a single zocecium. 



Tangential sections show a variety of appearances according to 

 the particular zone or zones represented in them. Sections cutting 

 across zocecia iust beneath the surface of an old branch often exhibit 



