BRYOZOA. 381 
Ceramophylla.] 
reminding of Ceramoporella inclusa (see pl. XXVIII, figs. 8-11). The lunarium, how- 
ever, is never prominent as in that species, nor is the posterior border of the aperture 
elevated as much as is usual among Lower Silurian ceramoporoids. Mesopores two 
or three to each zocecium, placed indiscriminately among the larger apertures or 
one on each side and a third in front of the zocecial orifice. 
This species is closely related to both D. vaupeli and communis Ulrich, of the 
Cincinnati group of Ohio, but it is clearly not identical with either. In the first 
place the Trenton form is always smaller, so that they may be distinguished at once 
by the matter of size alone. Then the lunarial rim is not so high and the arrange- 
ment of the mesopores and other superficial parts generally a little different. 
Formation and locality—In the upper third of the Trenton shales, and in the Galena shales at 
St. Paul and Cannon Falls. Also in the Trenton limestone at Trenton Falls, New York, and Ottawa, 
Canada. 
Genus CERAMOPHYLLA, n. gen. 
Zoaria erect, bifoliate, the two layers grown together back to back; in other 
respects like Ceramoporella and Diamesopora. 
Type: C. frondosa, n. sp. 
The leaf-like zoarium of the only species of this genus known, is in many 
respects very much like that of Rhinopora, Hall. Still they are very different struc- 
turally, and I am satisfied that the relationship between them must be quite remote. 
On the other hand, Ceramophylla may be justly called a bifoliate Ceramoporella, just 
as Diamesopora would be a ramose one. 
CERAMOPHYLLA FRONDOSA, 7. Sp. 
PLATE XXVIII, FIGS. 3-7 
Zoarium arising from a small basal expansion into erect, leaf-like, undulating 
fronds, celluliferous on both sides ; thickness varying from 0.5 to 2.0 mm., but aver- 
aging less than 1 mm.; largest frond seen about 40 mm. high; margins rounded, 
exposing the mesial lamine. At intervals of about 3 mm. the surface exhibits more 
or less conspicuous, substellate maculw of mesopores. Zocecial apertures ovate, 
oblique, the posterior margin well elevated, arranged more or less regularly in 
transverse and diagonally intersecting series, with about eight in 3 mm. Mesopores 
one, two, or three to each zocecium, variously arranged, often irregularly distrib- 
uted. Inthe most regular and normally developed examples the zocecial apertures 
