BRYOZOA, 131 
Rhinidicty a.) 
of the branches; in others, however, those forming the marginal row on each side 
may be turned slightly outward. Interspaces comparatively thick, less ridge- 
shaped than usual, often slightly zigzag, with the range of granules well developed. 
Internal structure chiefly diagnostic in vertical sections. These show that the 
primitive or prostrate cell is comparatively elongate, and that at the turn into the 
“vestibule” the wall is merely sharply curved and not angular, as in R. mutabilis. 
Associated with this species is a larger form, agreeing in all other respects quite 
closely with it. At first I thought it identical with R. mutabilis, and so figured it in 
1890 (Ill. Geol. Surv. Repts., vol. viii, p. 304, fig. 2, d, f, and g). At present [ should 
prefer regarding it as a variety of FR. neglecta. For the Canadian variety of this 
species see remarks under Rf. paupera. 
Compared with other species, Ff. nicholsont will be found to have grown differ- 
ently, the bifurcation of the branches being much less frequent ; the zocecial aper- 
tures are also more oblique, and vertical sections quite different... R. mutabilis has 
wider branches, more direct zocecial apertures, and different vertical section. 
Formation and locality.—Not uncommon in strata equivalent to the Galena limestone of the North- 
west, at Frankfort, Kentucky, and several localities in Boyle and Mercer counties of that state. Also in 
rocks of the same age at Nashville, Tennessee. Two fragments supposed to be identical with these 
Kentucky and Tennessee specimens were collected at St. Paul from the upper shales. 
Mus. Reg. No. 8104. 
Rurnipictya Exiaua Ulrich. 
PLATE VIII, FIGS. 6-10. 
Rhinidictya exigua ULRicH, 1890. Jour. Cin. Soc, Nat. Hist., vol. xii, p. 184, fig. 9. 
Zoarium bifoliate, small, growing from an expanded basal attachment. Lower 
portion of branches subcylindrical, with the zocecial apertures here largely filled with 
a smooth solid deposit of sclerenchyma. Above the first bifurcation the branches 
have become acutely elliptical in cross-section, their width varying from 0.5 mm. to 
1.2 mm., with parallel margins, the edges sharp, but in no case seeming to have 
more than just an appreciable non-celluliferous border. Zocecia in from three to 
seven rows on each face, their apertures, in the usual state of preservation, appear- 
ing as impressed, nearly direct, subelliptical or subquadrate, those in the central 
rows 0.2 mm. long by 0.1 mm. wide, those in the marginal row on each side of the 
branch sometimes a little larger and often directed somewhat obliquely outward ; 
all regularly arranged longitudinally, seventeen or eighteen in 5 mm., and separated 
from each other by rather-thin, seemingly smooth interspaces, the latter forming 
slightly elevated longitudinal ridges. In the specimens originally described and 
figured, the apertures are somewhat obscured by remains of the shaly matrix, but 
with several fragments lately discovered among my material from Fountain, Minn., 
