CORALS AND BRYOZOA. 
57 
HEMITRYPA, Phillips. 1841. 
Fenestella (Hemitrypa) biserialis. 
PLATE XXII, FIGS. 13, 16-18. 
Fenestella ( Hemitrypa ) biserialis, Hall. Thirty-second Rept. N. Y. State Mus. Nat. Hist., p. 174. 1S79. 
In part Fenestella ( Hemitrypa) biserialis, Hall. Report of State Geologist for 1SS2. Expl. pi. 22, figs- 
13—IS. 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 carinae, 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 XXII, FIGS. 14, 15. 
In part Fenestella ( Hemitrypa) biserialis, Hall. Report of State Geologist for 18S2. Expl. pi. 22, figs. 
13-18. 1883. 
Bryozoum infundibuliform, gradually expanded. Branches moderately slender, 
rounded or angular on the non-celluliferous free, and frequently with a strong 
