CAMBRO-SILUaiAN MICRO-PALiEONTOLOOY 9 



This species may be readily distinguished externally ivom MmticuUpora 

 CincinnatiensiSy Nicholson, to which it is most nearly related, by the 

 absence of monticules, which are a marked feature of that species ; and 

 internally by the very limited number of interstitial tubes. 



Locality and Formation.— llwW^ Que., near Ottawa City. Trenton Forma- 

 tion. 



Collector. — Walter JR. Billings, to whom the species is dodicated. 



MONTICULIPORA PARASITICA, Ulrich. 



Mont iculipora parasitica, Ulrich, Journ. Cincinnati Soc. Nat. Hist., Vol. 

 v., p. 238, pi. 10, figs. 3, 3a, 1882. 



The author is indebted to Mr. Ulrich for the identification of this species. 

 Locality and Formation. — Ottawa City. Trenton Formation. 

 Collector. — Walter E. Billings. 



HoMoTRYPA, Ulrich. 



" External Characters. — Zoarium ramose to subfrondescent ; surface 

 smooth, or with more or less prominent monticules. Cells circular^ ovate 

 or polygonal, with moderately thin walls. At intervals there arc groups 

 of larger sized cells, which again sometimes enclose small stellate macuUx), 

 consisting of much smaller, angular cells. The surface extensions of 

 spiniform tubuli may often bo observed at the angles of the colls. 



" Internal Characters. — In the axial portion of the branches or fronds, the 

 tubes are " immature," and may be crossed by straight diaphragms ; 

 usually diaj^hragms are entirely wanting in this region. The tube-walls 

 are excessively thin until they reach the peripheral regions, when they 

 arc much thickened, and bend outward to open at the surface. In the 

 peripheral or '' mature " portion of the zoarium, the tubes are provided 

 with a series of cystoid diaphragms; the space intervening between their 

 lloxuous inner lino, and the opposite wall of a tube, is crossed by equally 

 numerous straight diaphragms. The tube- walls are perforated by rather 

 large connecting foramina. In the tubcrculated species the spiniform 

 tubuli are numerous, but very small, and not easily recognized, while in 

 the smooth forms they are much larger^ and constitute a conspicuous 

 feature in sections. The internal structure of the small tubes, which form 

 the macuUc of some species, is not remarkably different from that of the 

 ordinary tubes. The only difference that I have been abio to detect is 

 found in the fact that cystoid diaphragms are but rarely devolopod in 

 them." Trenton and Cincinnati. (E. O. Ulrich, Journ. Cincinnati Soc. 

 Nat. Hist., Vol. v., p. 210, 1882.) 



