CORALS AND BRYOZOA. 
55 
over the greater portion of the frond. The summit of the carina has a width 
of .35 mm. 
In the normal condition of this species, the margins of the expanded summits 
of the carinrn have simply a row of nodes. In some specimens a few of the 
nodes extend and form lateral processes which unite with those opposite side 
connecting the summits of the carinae. Over the greater portion of one specimen 
all the nodes are thus extended and united giving to it the essential character 
of Unitrypa. This species shows the manner of growth of Unitrypa and its 
intimate connection with Fenestella ; also the impossibility of forming a dis¬ 
tinctly limited genus from these forms. 
Formation and locality. Lower Helderberg group, Near Clarksville, N. Y. 
Fenestella (Unitrypa) Nervia. 
PLATE XXII, FIGS. 1-3, 6, (9, 10)? 
Fenestella Nervia, Hall. Twenty-sixth Rept. N. Y. State Mus. Nat. Hist., p. 93. 1874. 
Hemitrypa prima, “ Twenty-sixth Rept. N. Y. State Mus. Nat. Hist., p. 98. 1874. 
Fenestella ( Hemitrypa) Nervia. Hall. Thirty-second Rept. N. Y. State Mas. Nat. Hist., p. 173. 1879. 
In part Fenestella (Hemitrypa) Nervia? Hall. Report of State Geologist for 1882. Expl. pi. 22, figs. 1-6, 
9, iO. 1883. 
Bryozoum infundibuliform, broadly spreading and radially undulated or folded. 
Branches moderately strong, rounded, granulose. Bifurcations frequent. 
Interstices narrower than the branches. Dissepiments strong, about six in 
the space of 5 mm. Fenestrules oval, width generally about one-half the 
length. 
On the celluliferous face the fenestrules usually appear much narrower than 
on the opposite side. Cell apertures in two ranges, small, circular, distant 
less than the diameter of an aperture; margins distinctly elevated, not 
indenting the borders of the fenestrules. Branches marked by strong, 
elevated carinae, which have their summits slightly expanded and connected 
by slender lateral processes. 
Width of branch above a bifurcation .33 mm., increasing to .50 or .60 mm.; 
width of dissepiments .35 mm.; length of fenestrules .50 mm. 
