464 PALAEONTOLOGY OF ILLINOIS. 



V 



CERAMOPORELLA Ulrich, 1882. 



("Amer. Pal. Bry." Jour. Cin. Soc. Nat. Hist. Vol. V, p. 156.*) 

 (For generic diagnosis see page 380.) 



This genus is intended to receive a number of Silurian JBryo- 

 zoa that most palaeontologists would refer to Ceramopora Hall. 

 But, as I have shown, C. imbricata, the type of the genus, 

 differs too widely from these forms to admit of being referred 

 to the same genus. 



Commencing in the upper half of the Trenton group with one 

 or two species, Ceramoporella is represented by six or seven 

 additional species in the Cincinnati group. Only three of these 

 are here described, while Nicholson's Ceramopora ohioensis is, 

 provisionally, also placed here. It is questionable whether the 

 genus is represented in Upper Silurian rocks. Some of the 

 species from that horizon, that have been described under Ce- 

 ramopora, present a close external resemblance to C. distincta, 

 yet I am inclined to believe that a careful examination of their 

 interiors will reveal Fistuliporoid characters. 



CERAMOPORELLA DISTINCTA Ulrich. 



PL XXXIX, flg. 6, 6a. 



Zoarium forming thin, parasitic expansions upon Monticuli- 

 poroids or Orthocerata; by the formation of successive super- 

 imposed layers, large masses may result. The layers vary in 

 thickness from 0.5 to 1.0 mm. Surface even, though sometimes 

 appearing monticulose owing to the zoarium adapting itself to 

 the irregularities of the surface to which it is attached. Zooecia 

 thin-walled, at first prostrate, then becoming abruptly direct 

 or almost so, more or less triangular or pyriform, and with 

 well marked lunaria. In young examples very oblique, almost 

 imbricating. Apertures with thin obliquely projecting peristome, 

 more elevated posteriorly, oval in shape, about 0.2 mm, in 



* A description of this genus was published as above cited in the synopsis of classi- 

 fication that appeared in the first part of my "American Palaeozoic Bryozoa." Unfortu- 

 nately, the publication of this memoir was discontinued ere I could take up the CEKAMO- 

 PORID.S:. As no good species of the genus was then described I could not name a type. 

 Hence the genus was not actually established, and ought, perhaps, to date from this 

 work. 



