ORDER I 



CYCLOSTOMATA 



267 



IDitaxia, Hagw. Zoaria ramose, brandies 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 zooecia. Jura. 



Neuropora, Bronn (Chrysaora, Lam. ; Filicava, d'Orb.), (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, d'Orb. Zoaria ramose, consisting of but one kind of zocecial 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 zocecia, larger 

 than the average, occur at regular intervals. Zooecial 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, aliL-ays irregular, and usually without diaphragms. A few horizontal 

 diaphragms of ten present in the zocecial tubes. Walls minutely porous, composed of intimately 

 connected and irregularly 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 

 Berenicca and Apsendcsia ; 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 



FIG. 435. 



Ceramoporella distinctu, 

 Ulrich. Lower Trenton, 

 Minnesota. Surface of para- 

 sitic expansion, is/, (after 

 Ulrich). 



FIG. 436. 



Crepipora perampla, Ulrich. Trenton; Minnesota. A, Vertical section. 

 -R, Transverse section, ?/]. C, Same, "/j, showing lunaria. D, Surface of C. 

 simulans, Ulrich, 9fr (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 



