20 BRYOZOAN FAUNA OF THE ROCHESTER SHALE. 
Vertical sections show that the walls of the tubes are at first thin but thicken in the 
mature region where the characteristic indefinite structure and the pore-like openings are 
well exhibited. Diaphragms wanting. In tangential sections the large, well-defined 
lunarium projecting in the zooecial cavity is the special feature, while the ovate zooeeia, 
irregular mesopores, and indefinite wall structure are also well brought out. 
With the exception of Ceramopora imbricala and C. labecula, all of the Niagaran species 
described by Hall under Ceramopora appear to be fistuliporoids. The free zoarium of 
C. imbricaia and the small attached disks of C. labecula are differences in growth that will 
readily distinguish them from the species here described. The open mesopores, strongly 
arched, prominent lunaria, and radiating zooeeia present an appearance so different from 
associated bryozoa that this is not likely to be confused with any other species. 
Occurrence. — Not uncommon in the Rochester shale at Rochester and Lock port, N. Y., 
and at Grimsby, Ontario. Rare in the Osgood beds at Osgood, Ind. 
Catalogue numbers, 35735, 35736, U. S. National Museum. 
Genus CERAMOPORELLA Ulrich. 
Zoarium of incrusting layers, which by superposition may form masses; zooeeia short, 
tubular, with thin walls; apertures oval, oblique, the lunarium forming a hood; mesopores 
abundant, often completely encircling the zooeeia. 
Hitherto this generic type lias been supposed to have been restricted to the Ordovician, 
but the following species possess all of the features of the genus. 
Ceramoporeli.a orbiculata (Ringueberg). 
PI. IX, figs. 12-15. 
Ceramopora orbiculata Ringueberg, Bull. BulTalo Soc. Nat. Hist., V. 1886, p. 19, pi. 2, figs. 13, 13a. 
Original description.— Habit parasitic, small, flat, discoid, central portion slightly elevated, from 
which point the lip of a lamination extends outward and curving backward to the outer border of the 
disk, showing that it increased by growing upon itself in spiral laminae, and gives no evidence of any 
further lateral extension, ("ells closely arranged, directed outward from the center at an oblique angle 
tending in the direction of the spiral growth, and have a prominent nariform calice over the upper side. 
Outer border of disk striate. 
From the upper part of the shale. 
The specimen described and figured by Ringueberg proved upon examination to be the 
young of a Ceramoporella, at first supposed by the writer to be a new species. These small 
incrusting disks are not uncommon in the shales, and a careful study of their zocecial 
characters will usually determine their relations to older specimens. Most of the various 
ceramoporoids and fistuliporoids commence their growth as small incrusting disks which 
appear quite distinct and often seem to bear no relation to the mature form. The following 
are the characters of Ringueberg's species as observed in mature specimens. 
Zoarium of thin parasitic incrustations seldom exceeding 0.40 mm. in thickness. Sur- 
face smooth, exhibiting at intervals of 2 to 2.5 mm. small, solid maculae from which the 
zooeeia radiate. Zooecial apertures round to oval, placed at the bottom of vestibular areas 
formed by thin coalescing ridges occupying the interspaces. About 10 zooeeia in 2 mm. 
Lunaria crescentic, small but prominent, occupying about one-sixth of the vestibular perim- 
eter, and with the ends projecting slightly into the zooecial cavity. The vestibular areas 
are polygonal in outline, usually quadrangular when the radiate arrangement is pronounced, 
and bear the lunaria on the angle nearest a macula. 
A perfect specimen of this neat little species with its radiating zooeeia and prominent 
lunaria forms one of the prettiest bryozoans of this formation. The extremely small 
zooeeia, polygonal outline of the vestibules, small crescentic lunarium, and the radiate, 
almost diagrammatic arrangement of the zooeeia about the maculae are characters which will 
cause this form to be easily identified. 
Occurrence. — Not uncommon in the Rochester shale at Lockport, Rochester, Lewis! on, 
and Niagara Falls, N. Y., and at Grimsby, Ontario. 
Catalogue numbers, 35478, 35479, 35737, U. S. National Museum. 
