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 carinas 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 carinas. 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 locMliti/. Lower Helderberg group, Near Clarksville, N. Y. 



Fenestella (Unitrypa) Nervia. 



PLATE XXU, FIGS. 1-3, 6, (9, 10) ? 



FemenUlla Nervia, Hall. Twenty-sixth Kept. 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 Mus. Nat. Hist., p. 173. 1879. 

 In part Fenestella (Heiaitrypa) Nerniaf Uall. Report of State Geologist for 1882. Expl. pi. 22, figs. 1-6, 



9, lO. 1883. 



Bryozoum infundibuliform, broadly spretuling 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 fivce 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 carinas, wliich 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. 



