BRYOZOA. 331 



CeramophyUa.] 



reminding of Ceramoporella inclusa (see pi. XXVIII, figs. 8-11). The lunarium, how- 

 ever, is never prominent as in that species, nor is the posterior border of the aperture 

 elevated as much as is usual among Lower Silurian ceramoporoids. Mesopores two 

 or three to each zooecium, placed indiscriminately among the larger apertures or 

 one on each side and a third in front of the zooecial orifice. 



This species is closely related to both D. vaupeli and communis Ulrich, of the 

 Cincinnati group of Ohio, but it is clearly not identical with either. In the first 

 place the Trenton form is always smaller, so that they may be distinguished at once 

 by the matter of size alone. Then the lunarial rim is not so high and the arrange- 

 ment of the mesopores and other superficial parts generally a little different. 



Formation and locality.— In the upper third of the Trenton shales, and in the Galena shales at 

 St. Paul and Cannon Falls. Also in the Trenton limestone at Trenton Falls, New York, and Ottawa, 

 Canada. 



Genus CERAMOPHYLLA, n. gen. 



Zoaria erect, bifoliate, the two layers grown together back to back; in other 

 respects like Ceramoporella and Diamesopora. 



Type: G.frondosa, n. sp. 



The leaf-like zoarium of the only species of this genus known, is in many 

 respects very much like that of Bhinopora, Hall. Still they are very different struc- 

 turally, and I am satisfied that the relationship between them must be quite remote. 

 On the other hand, CeramophyUa may be justly called a bifoliate Ceramoporella, just 

 as Diamesopora would be a ramose one. 



Ceramophylla frondosa, n. sp. 



PLATE XXVIII, PIGS. 3-7. 



Zoarium arising from a small basal expansion into erect, leaf -like, undulating 

 fronds celluliferous on both sides ; thickness varying from 0.5 to 2.0 mm., but aver- 

 aging less than 1 mm.; largest frond seen about 40 mm. high; margins rounded, 

 exposing the mesial laminae. At intervals of about 3 mm. the surface exhibits more 

 or less conspicuous, substellate maculae of mesopores. Zooecial apertures ovate, 

 oblique, the posterior margin well elevated, arranged more or less regularly in 

 transverse and diagonally intersecting series, with about eight in 3 mm. Mesopores 

 one two, or three to each zooecium, variously arranged, often irregularly distrib- 

 uted In the most regular and normally developed examples the zooecial apertures 



