BRYOZOA. 329 



Ceramoporella inelusa.l 



in 3 mm. Apertures very oblique, with an overhanging hood, highest posteriorly. 

 Mesopores numerous, small, usually forming a single linear series between the sides 

 of the zooecia. 



This species is much rarer than the associated C. inclusa from which it is at 

 once distinguished by its smaller and differently shaped zooecial 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, n. sp. 



PLATE XXVIII. FIGS. 8-11. 



Zoarium forming thin crusts over foreign bodies, not observed to consist of 

 more than a dingle layer, less than 1 mm. thick, generally 20 mm. or more in 

 diameter. The customary maculae, about which the zooecial 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. Zoo3cial 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 3 mm. 



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 zooecial 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 Fillniore counties. Rare and less typical in 

 the upper third of the shales at St. Paul and Cannon Palls. 



Mus. Keg. Nos. 7624, 7656, 7661, 7662, 8380. 



