ORDER I CYCLOSTOMATA 267 
? Ditawia, Hagw. Zoaria ramose, branches flattened, consisting of two layers of 
tubes grown together back to back. Otherwise like Heteropora, Cretaceous. 
Chilopora, Haime. Zoaria erect, lamelliform ; apertures rather large, rounded 
or sub-triangular, oblique, with the lower half of the margin elevated. Interstitial 
cells numerous, much smaller than the zowcia. Jura, 
Neuropora, Bronn (Chrysaora, Lam. ; Filicava, VOrb.), (Fig. 434). Zoaria generally 
irregularly ramose, attached at the base, composed of sub-equal tubular zocecia. These 
open on all exposed parts of the surface, save on certain variously arranged, more or 
less raised, thin solid ridges. Jura and Cretaceous. 
Acanthopora, VOrb.  Zoaria ramose, consisting of but one kind of zoccial tubes. 
Surface studded with numerous solid conical or spine-like prominences. Jura and 
Cretaceous. 
Families doubtfully referable to the Cyclostomata.’ 
Family 9. Ceramoporidae. Ulrich. 
Zoaria usually encrusting, sometimes discoid, lamellate, massive, or forming more or 
less regular hollow branches ; rarely bilobiate. Clusters of mesopores and of zowcia, larger 
than the average, occur at regular intervals. Zowcial apertures usually oblique, of sub- 
triangular, ovate, or polygonal form; lunarium present, appearing at the surface as a 
prominent overarching hood, or as a slightly elevated portion of the margin, of crescentic 
form, with the ends projecting more or less into the aperture. Mesopores or interstitial cells 
generally present, always irregular, and usually without diaphragms. A few horizontal 
diaphragms often present in the zoecial tubes, Walls minutely porous, composed of intimately 
connected and irreqularly laminated tissue. Ordovician and Silurian. 
This is one of the largest and most important of the families of Palaeozoic Bryozoans, and is 
especially common in the Trenton and Cincinnati Groups. The earliest forms resemble 
Berenicea and Apsendesia ; while Ceramoporella, Chiloporella; and especially Bythotrypa, may 
be regarded with reasonable confidence as the progenitors of the Fistuliporidae. At any rate 
the connection between the two families is so intimate as to forbid any wide separation. 
Ceramopora, Hall. Discoidal, free, or attached by the centre of the base. Under 
surface with one or more layers of small irregular cells. Zocecia opening on the upper 
A B C 

Fic. 435. 

Ceramoporella  distincta, 
Ulrich. Lower Trenton, 

Minnesota. Surface of para- Crepipora perampla, Ulrich. Trenton; Minnesota. A, Vertical section. 
sitic expansion, 12/; (after B, Transverse section, 7/;. C, Same, 14/;, showing lunaria. D, Surface of C. 
Ulrich). simulans, Ulrich, 9/; (after Ulrich). 
surface, large, oblique, imbricating, and radially arranged about the depressed centre. 
Mesopores irregular, short, numerous at the centre of the colony, decreasing toward the 
periphery. Silurian. 
Ceramoporella, Ulrich (Fig. 435). Zoaria encrusting, becoming massive by super- 
imposition of numerous thin layers. Zocecial tubes short, walls thin, apertures more 
