CORALS AND BRYOZOA. 145 



On the celluliferous face the dissepiments are angular, on a plane with the 

 branches. Fenestrules of about the same appearance as on the opposite face. 

 Cell apertures in two ranges, opening directly outward, disposed around the 

 fenestrules, there being two apertures on each dissepiment, seven or eight 

 apertures around each fenestrule : margins distinctly elevated but not in- 

 denting the borders of the fenestrule. Branches and dissepiments carinated, 

 connected, carina about .50 mm. in height, at first very thin, but immediately 

 expanding and giving an appearance very similar to the non-celluliferous 

 face of the frond ; carinse of branches about .30 mm. in width, gently en- 

 larging before bifurcation, angular, slightly carinated; dissepiments .45 mm. 

 wide, angular, slightly carinated, on a plane with the branches ; interstices 

 • broiidly oval. This surface, if seen from above, would be very easily mis- 

 taken for the non-celluliferous face of some frond. 



This species very nearly resembles F. (L.) perforata of the Hamilton group, 

 but the frond is coarser, the fenestrules larger, the dissepiments less frequent ; 

 there being only two in the same space occupied by three or four in that species. 



Formation and locality. Upper Helderberg gx'oup, Walpole, Ontario, Canada. 



I. Forms having the carina connected by scalm which meet midway between the carince, 

 of adjacent branches, forming a pseudo-carina. 



HE MITRYP A, Phillips. 1841. 



FeNESTELLA (HeMITRYPA) CRIBR08A. 



NOT FIUDRUD. 



Fetuitella {Hemitrypa) cribrota. Hall. Trans. Albany Institute, vol. x, abstract, p, 35. 1881. 



Bbtozocm infundibuliform. Branches slender, width above a bifurcation .30 

 mm., increasing to .50 mm., more or less rapidly expanding, arising from a 

 thin, broadly spreading, striated base, incrusting other objects. The pedicel 

 is of uniform appearance and char.acteristic, usually having a length of about 

 5 mm., and a nearly constant diameter of a little more than 2 mm. ; the 

 branches extend its entire length, and when well preserved they are 

 generally rounded, but sometimes angular, frequently concave below a bifur- 

 cation, with numerous small, elongate, narrow nodes, which are sometimes 



