130 THE PALEONTOLOGY OF MINNESOTA. 
{Rhinidictya. 
peristome ; (2) the interspaces on the whole are thicker, while the elevated lines 
enclosing the depressed quadrangular spaces in which the apertures are situated, are 
sharper; (8) the arrangement of the apertures between longitudinal lines prevails 
throughout, there being no oblique rows; and (4) while the width of the branches is 
about the same or greater (the average is very nearly 1.5 mm.); there are only seven 
to nine rows of cells instead of ten to twelve. In all these respects, however, the 
Canadian form agrees more closely with R. neglecta, but before I commit myself def- 
initely upon the matter of their true relations I shall want to institute careful 
comparisons of their respective internal characters—a step that I am not yet pre- 
pared to make. Still, in the meantime, it may be desirable occasionally to refer to 
the Canadian form, in which case a distinctive appelation would be convenient. I 
propose, therefore, the provisional designation Rhinidictya neglecta, var. canadensis. 
Comparing RP. pawpera (sens. strict.) with other species of the genus, we find that it 
is distinguished from R. mutabilis by its smaller zoarium, narrow and more frequently 
dividing branches, more numerous zocecia in a given space, and the greater differen- 
tiation in the direction of the central and marginal zocecial apertures ; from R. trenton- 
ensis and R. nicholsoni in much the same features, though in a different degree. To 
them is to be added, for the former, that its zocecial apertures are not only much 
larger, but more nearly quadrate or hexagonal, with the longitudinal ridges between 
them nearly or quite obsolete ; and for the latter, that its zocecial apertures are 
more oblique. &. exigua is very close, differing mainly in its narrower branches and 
less oblique arrangement of its zocecial apertures in the marginal rows. 2. minima 
has thicker and more ornamental zocecial interspaces, and differs internally in hav- - 
ing the superior hemiseptum well developed. 
Formation and locality——Not uncommon in the upper third (‘‘Phylloporina beds”) of the Trenton 
shales, at St. Paul and south of Cannon Falls, Minnesota, and Decorah, Iowa. Probably also in the 
Galena at Neenah, Wisconsin. 
Mus. Reg. Nos. 5935, 7564, 7612. 
RHINIDICTYA NEGLECTA, 2. Sp. 
PLATE V, FIGS. 22-25 
Stictopora paupera (part.) ULRICH, 1886, Fourteenth Ann. Rept. Geol. Nat. Hist. Sur. Minn., p. 69. 
Zoarium small, branches dividing dichotomously at intervals of from 4 to 7 mm., 
rather convex, the margins parallel, not very sharp, and with the non-celluliferous 
border variable. Width of branches rather constant at about 1.5 mm. Zocecia in 
eight to eleven ranges, the usual number nine, with rather small, elliptical ; oblique 
apertures, about seventeen in 5 mm. lengthwise, and 6in 1 mm. transversely. In 
most cases all the apertures are directed longitudinally or parallel with the edges 
