I 



\ 



b 



CORALS AND BRYOZOA. 141 



same direction, two in the space of 5 mm. Summits of carinse very thin, 

 sometimes distinct and straight, at other times interrupted and obscured by 

 the scalae ; under these conditions this face of the frond appears to be com- 

 posed of oblique, imbricating, walled cells. Fenestrules oval, length 1.25 

 mm., width .70 mm. 



This species may be distinguished from F. (U.) pernodosa by the size of the 

 branches and fenestrules and in the character of the ornamentation of the 

 branches; from F. (U.) accHvis by the larger size and more distant branches 

 and dissepiments, and from all other species at present known by the character 

 of the seal as. 



Formation and locality. Upper Helderberg group, Walpole, Ontario, Canada. 



Fenestella (Unitrypa) fastigata. 



PLATE LIV, KIGS. 1-8. 

 Fenettdla (Hemitrypa) fastigata. Hall. Trans. Albany Institute, vol. x, abstract, p. 36. 1881. 



Brvozoum infundibuliform. Branches slender, width above a bifurcation .25 

 mm., increasing to .35 or .40 mm., very gradually enlarging, for the greater 

 portion of their length of essentially the same size, angular, carinated ; carina 

 slight, but distinct. Interstices of the same width as the branches. Dissepi- 

 ments comparatively strong, width .25 mm., flat or angular, on a plane with 

 the branches, six in the space of 5 mm. Fenestrules oval, length .55 mm., 

 width .30 mm. Very frequently there is a narrow elevation on the dissepi- 

 ments and branches surrounding the fenestrules. 



On the celluliferous face the dissepiments are rounded, much depressed. 

 Fenestrules narrower than on the opposite face. Cell apertures in two ran- 

 ges, opening outward, twenty in the space of 5 mm., separated by half the 

 diameter of an aperture : margins elevated, strongly indenting the borders of, 

 and partially obscuring the fenestrules. Carina thin, height 1 mm. Scalae 

 very thin, curved, oblique, the direction being away from the base, lower 

 portion the stronger, not bent, seven in the space of 5 mm. Summits of 

 carinas very thin, not elevated above the scalae. Interstices nearly circular. 



