Or 
BRYOZOA, OAR 
Calloporide.] 
with a gentle curve, the walls become thickened and the diaphragms more abund- 
ant, the intervals between the latter varying here from one-fourth to one tube- 
diameter, with seven in 1 mm. measuring from the surface of a fully developed 
example. Acanthopores originating in the outer part of the axial region, large and 
readily distinguished. Tangential sections with the walls rather thick and consist- 
ing of a central space, generally of light color, representing the original walls, and 
a dark ring-like deposit immediately about the zocecial cavities. On the whole the 
structure and thickness of the walls is much as in Dekayella prenuntia, var. simplex 
(pl. XXII, figs. 41 and 42). The acanthopores are isolated, occupying the points of 
junction between every three, four or five zocecia. Their large size makes them very 
conspicuous in sections passing through deeper levels in which the walls are thinner 
than described. 
In this species the diagnostic characters of Dekayia are not yet fully developed, 
the diaphragms being too numerous. A revision of the Heterotrypide would prob- 
ably remove it to Dekayella. A more typical, but undescribed species, with fewer 
diaphragms and smaller acanthopores, is sometimes associated with D. trentonensis 
in the Galena shales. Dekayella echinata, which at first I confounded with the 
present species, has more numerous diaphragms, thinner walls, and a small set of 
acanthopores. 
Formation and locality.—Rather rare in the upper third of the Trenton shales and in the overlying 
Galena shales at St. Paul, and near Cannon Falls, Minnesota. The original types are from the shaly por- 
tion of the Trenton at Burgin, Kentucky. The species is to be found also at Frankfort and other localities 
in that state, associated with Prasopora simulatrix Ulrich. 
Family CALLOPORIDAS, Ulrich. 
Genus CALLOPORA, Hall. 
Callopora, HALL, 1852, Pal. N. Y., vol. ii, p. 144, and 1887, Pal. N. Y., vol. vi, p. xv; NICHOLSON, 1874, 
Pal. Ontario, p. 61, and Geol. Mag., n.s., vol. i, p. 18; ULRicH, 1882, 
Jour. Cin. Soc. Nat. Hist., vol. v, pp. 154 and 251; also 1890, Geol. Sur. 
Tl., vol. viii, pp. 372 and 416; ForrsTE, 1887, Bull. Sci. Lab. Denn. 
F Univ., vol. ii, p. 172. : 
?Callopora, DYBOWSKI, 1877. Die Chetetiden, p. 106. 
Zoarium usually ramose, rarely subfrondescent, or pyriform; surface smooth or 
tuberculated. Zoccial tubes with thin walls, varying according to the number of 
mesopores from circular or oval to polygonal in cross-section. Apertures closed in 
the perfect state by centrally perforated and often radially marked or ornamented 
plates, which are left behind as growth proceeds to form floors (diaphragms) of 
succeeding layers. Mesopores angular or rounded, more or less numerous, some- 
times surrounding the zocecia; closely tabulate. Zocecial tubes attaining their full 
