CORALS AND BRYOZOA. 121 



zig-zag, anastomosing, and having a prominent conical node at the points of 

 junction. Interstices more than twice the width of the branches. Width 

 of anastomosed portion a little less than .50 mm., three in the space of 5.50 

 mm. Fenestrules regularly oval, length about 1.30 mm., width .75 mm. 



On the celluliferous face the branches are sharply rounded, connected by 

 short dissepiments which are rounded and very much depressed. Fenestrules 

 much narrower than on the opposite face, the interstices being only a 

 little wider than the branches. Cell apertures in two ranges, opening a 

 little laterally, seventeen in the space of 5 mm., separated by about the 

 diameter of an aperture. Surface between ranges of apertures carinated ; 

 carina thick, height about .50 mm. 



This species closely resembles F. {Reteporina) rhombifera, but the dissepiments 

 are a little narrower and the carina is smooth ; the carina of that species has a 

 row of small nodes on each margin of the summit; the non-celluliferous face 

 so closely resembles some forni.s of that of F. striata of the Hamilton group, that 

 it is very difficult to satisfactorily distinguish them ; on the celluliferous face 

 the carina is much thicker and higher. 



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



c. Forms having prominent carina with expanded summits. 

 Fenestella lunulata. 



PLATE XLVII, FIGS. I-IO. 



Flmestella lunulata, Hai.l. Trans. Albany Institute, vol. x, abstract, p. 31. 1881. 

 Semicoscinium Miqitatum, Ulrich Cont. Am. Pal., vol. 1, No. 1, p. 13, pi. 1. 1886. 



Beyozoum infundibuliform, frequently of irregular growth, sometimes twisted 

 or involved. Branches very slender, width above a bifurcation .25 mm., 

 increasing to .45 mm., rounded or sub-cangular, often irregular. Interstices 

 of about the same width as the branches. Dissepiments strong, width from 

 .25 to .40 mm., oblique, having on the summit a prominent lunate elevation, 

 which extends upon the branches, the extremities connecting with the eleva- 

 tions of adjacent dissepiments, obscuring the branches, and sometimes giving 

 to the frond the appearance of being composed of oblique walled cells. On 



