BRYOZOA. 329 
Ceramoporella inclusa.] 
in3mm. Apertures very oblique, with an overhanging hood, highest posteriorly. 
Mesopores numerous, small, usually forming a single linear series between the sides 
of the zocecia, 
This species is much rarer than the associated C. inclusa from which it is at 
once distinguished by its smaller and differently shaped zocecial apertures. In C. 
interporosa the apertures are larger and more direct. 
Formation and locality—Lower third of the Trenton shales at Minneapolis and St. Paul. It is 
met with next in the Cincinnati rocks, being an abundant species at that locality. 
CERAMOPORELLA INCLUSA, ”. SP. 
PLATE XXVIII, FIGS, 8-11. 
Zoarium forming thin crusts over foreign bodies, not observed to consist of 
more than a single layer, less than 1 mm. thick, generally 20 mm. or more in 
diameter. The customary macul, about which the zowcial apertures are arranged 
in a radial manner, are represented, but less distinctly than usual. Nor is the 
radial disposition of the apertures as marked a feature as usual. Indeed, it is 
common to find, as shown in figure 8, all of them turned toward the nearest 
margin of the zoarium. Zocecial apertures oval, occupying, with three mesopores, 
the bottom of subtriangular or rhomboidal, obliquely depressed spaces. One of 
these mesopore-pits is in front, the second and third on the sides of the true aperture, 
the posterior side of the latter being formed by the strongly elevated lunarium 
which in this species is an unusually prominent feature. Arrangement of apertures 
only moderately regular, eight or nine in 3mm. ; 
Numerous deviations from the above described normal characters of this species 
are shown in the abundant material before me. Most of them are due to imperfect 
preservation and irregularities of growth, and all of them are of a nature that can 
be interpreted successfully only by extended study of specimens. 
The inclusion of each zoccial aperture and mesopores in a subtriangular en- 
closed space, and the strong development of the lunarium are distinctive for the 
species. These features are less constant in what I presume to be a mutation of the 
species (toward the Cincinnati group C. ohioensis Nicholson) occurring in the upper 
third of the Trenton shales. 
Formation and locality—Common in the lower and middle thirds of the Trenton shales at 
Minneapolis, St. Paul, and various localities in Goodhue and Fillmore counties. Rare and less typical in 
the upper third of the shales at St. Paul and Cannon Falls. 
Mus. Reg. Nos. 7624, 7656, 7661, 7662, 8380. 
