BRYOZOA. 141 
Phyllodictya.] 
then learned to esteem caution, the present less positive stand on the question will 
suffice till we have been informed of the minute structure of Hall’s types. These 
were derived from the northern part of Wisconsin, and if they prove to be identical 
with the specimens here described, a considerable extension of the geographical 
range of the species will result. The species is an important one too, in being 
highly characteristic of one horizon. 
Formation and locality.—In Minnesota known only from the upper third of the Trenton shales, at 
St. Paul. In Kentucky, rather common in the shales above the ‘‘ Modiolopsis beds.” In Tennessee it 
holds the same horizon (Safford’s Middle Nashville Series) at Nashville. 
Mus. Reg. No. 5942. 
Genus PHYLLODICTYA, Ulrich. 
Phyllodictya, ULRICH, 1882, Jour. Cin. Soc. Nat. Hist., vol. v, p. 153; MILLER, 1889, North Amer. 
Geol. and Pal., p. 315; Unricn, 1890, Geol. Surv. Ill., vol. viii, p. 390. 
Zoaria bifoliate, simple or iregularly branched, growing from an expanded basal 
attachment. Zocecial tubes long, with complete diaphragms but no hemisepta ; from 
the central axis they bend outward very gradually, causing the apertures to be more 
or less strongly oblique, with the posterior edge raised lip-like. Interspaces wide, 
subsolid, transversed vertically by one or two rows of minute tubuli, which appear 
as so many papille at the surface. 
Type: P. frondosa Ulrich. 
This genus requires more study before the relations to Hurydictya on the one 
side, and Pachydictya on the other, can be determined and satisfactorily established. 
The questions involved are rendered difficult of solution by the commingling of 
characters found in Pachydictya splendens Ulrich. and P. firma Ulrich, of the upper 
beds of the Hudson River group, and Eurydictya multipora (? Hall) of the Trenton 
group. All three of these species have certain features in common that do not per- 
tain to the more typical forms of either Pachydictya or Hurydictya. It is, however, 
precisely in those characters that these species remind us of Phyllodictya.* Though 
having an abundance of specimens of, at any rate the majority of the species, bear- 
ing directly upon the points at issue, I have been obliged, chiefly because of a lack 
of time, to defer pushing my investigations to a satisfactory conclusion. I realized 
also that all partial studies of the group of bifoliate Bryozoa, and consequent rear- 
rapgements of species, are only too likely to prove premature and faulty when the 
full results of a complete study of the group shall have become available. For the 
present it is sufficient to point out the obscure and perhaps weak spots in the classi- 
fication now in use. 
*Another genus presenting points of agreement with Phyllodictya is Ptilotrypa Ulyich, founded upon a single species 
from the upper beds of the Hudson River group, But the absence of “median tubuli” in the latter is a difference of 
such importance that the two genera must be regarded as widely distinct and as belonging to different families, 
