62 PALEONTOLOGY OF NEW YORK. 



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

 ward, twenty in the space of 5 mm., separated by less than the diameter of 

 an aperture: margins elevated, not, indenting the borders of the fenestrules. 

 Branches bearing prominent carinae which are expanded and angular along 

 their summits. 



Width of branches above the bifurcations .33 mm., increasing to .75 mm.; 

 diameter of dissepiments .25 mm. ; fenestrules varying from .60 to .75 mm. 

 in length and from .40 to .60 mm. in width ; height of carina .40 mm. 



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



Fenestella Idalia. 

 plate xxi, figs. 6-9. 



FentKieUa Idalia, Hall. Twenty-sixth Rept. N. Y. State Mus. Nat. Hist., p. 95. 1874. 

 Thirty-second Rept. N. Y. State Mus. Nat. Hist., p. 170. 1879. 

 Report of State Geologist for 1882. Expl. pi. 21, figs. 6-9. 1883. 



Bryozoom infundibuliform, broadly spreading, nearly flat for a short distance 

 above the base. Branches moderately slender, rounded, compactly arranged, 

 regularly increasing in size to the bifurcations, marked by from three to five 

 granulose striations on each branch ; sometimes so strongly granulose as to 

 ob.scure the striaB. Bifurcations frequent. Interstices usually about the 

 width of the branches. Dissepiments very slender, sub-angular, from six to 

 nine in the space of 5 mm., very slightly expanding at their junction, and 

 on the same plane with the branches. Fenestrules sub-quadrangular, occa- 

 sionally oval. 



On the celluliferous face the branches are angular, or sub-carinated. Dis- 

 sepiments angular and much depressed. The fenestrules appear narrower 

 than on the opposite face. Cell apertures usually in two ranges, circular, 

 opening somewhat laterally and separated by less than the diameter of an 

 aperture : margins elevated, indenting the borders of the fenestrules. 



Width of branch above a bifurcation .20 mm., increasing to .50 mm. ; 

 diameter of dissepiments .16 mm. ; length of fenestrules on different speci- 

 mens varying from .40 to .50 mm., width from .25 to .40 mm. 



