CORALS AND BRYOZOA. 57 



HEMITRYPA, Phillips. 1841. 

 Fenestella (Hemitrypa) biserialis. 



PLATE XXII, riGS. 13, 16-18. 



Eenettdla (Hemitrypa) biserialig. Hall. Thirty-second Rept. N. Y. State Mus. Nat. Hist., p. 174. 1879. 

 In part Fenentella {Hemitrypa) biserialis. Hall. Report of State Geologist for 1882. Expl. pi. 22, figs. 



13-18. 1883. 



Bryozoum infundibuliform, regularly expanding. Branches strong, rounded, 

 marked on the non-celluliferous face by single, prominent, triangular nodes, 

 which usually occur opposite the dissepiments. Interstices usually narrower 

 than the branches. Dissepiments strong, rounded, slightly depressed. 

 Fenestrules small, oval, width about one-half the length. 



On the celluliferous face the branches are angular, and the dissepiments 

 rounded and depressed. The fenestrules appear narrower than on the oppo- 

 site face. Cell apertures small, circular, in two ranges, opening directly out- 

 ward, twenty in the space of 5 mm., distant less than the diameter of an 

 aperture. Branches bearing strong carinoe, which are expanded along their 

 summits, sending off processes, which, meeting with similar processes from 

 the adjacent carinae, coalesce midway between the branches forming a ridge, 

 which is not so strong as the summits of the carinae. There are four pro- 

 cesses in the space of 1 mm. Interstices formed by the connecting bars sub- 

 quadrangular, width greater than the length. 



Width of branch above a bifurcation .30 mm., increasing to .50 or .60 mm. ; 

 dissepiments from 40 to .45 mm in diameter; fenestrules about .45 mm. long. 



Formation and locality. Lower Helderberg group, near Clarksville, N. Y. 

 Fenestella (Hemitrypa) biserialis, var. exilis, n. var. 



PLATE XXn, FIG.S. U, 15. 



In part Fenestella (Hemitrypa) biserialis, Hall. Report of State Geologist for 1882. Expl. pi. 22, figs. 



13-18. 1883. 



Bryozoum infundibuliform, gradually expanded. Branches moderately slender, 

 rounded or angular on the non-celluliferous face, .and frequently with a strong 



