56 PALEONTOLOGY OF NEW YORK. 



The elevated carinae with the connecting bars are very fragile and are want- 

 ing on the greater portion of the specimens observed. 



Formation and locality. In the shaly limestone of the Lower Helderberg group, 

 Clarksville, N. Y. 



Fenestella (Unitrypa) Nervia, var. constbicta. 



FLATB XXII, FIQS. 11, U. 



Feiuttdla (HemUrypa) ytrtia, var. (muitricta. Hall. Thirty-second Rept. N. Y. State Mus. Nat. Hist., p. 



174. 1879. 

 " " " .... Report of State Geologist for 1882. Expl. pi. 23, figs. 



11, 12. 1883. 



Beyozocm infundibuliform, compact. Branches moderately strong, slightly 

 diverging, es.sentially parallel, very gradually increasing in size to the bifur- 

 cations, marked on the non-poriferous side by from three to six strongly 

 granulose striae. Transverse section of branch broadly oval. Bifurcations 

 infrequent. Interstices narrow. Dissepiments rounded, granulose, very 

 slightly depressed, about eight in the space of 5 mm. Fenestrules oval, width 

 from one-half to three-fourths the length. 



On the celluliferous face the branches are angular and the dissepiments 

 much depressed. Cell apertures small, sub-circular, in two ranges, opening 

 somewhat laterally, twenty-five in the sp.ace of 5 mm., distant less than the 

 diametei* of an aperture : margins strongly elev.ated on the anterior, indent- 

 ing the borders of the fenestrules. Branch bearing a very thin carina, which 

 is slightly expanded along the summit and connected by irregular lateral 

 processes, which sometimes continue from the summit of one carina to that 

 of another ; at other times they meet midway, coalesce and form an indis- 

 tinct, irregular ridge. 



Width of branch above a bifurcation .40 mm., increasing to .60 mm. Dis- 

 sepiments from .20 to .25 mm. in diameter ; fenestrules about .40 mm. long ; 

 height of carina .40 mm., summit .14 mm. wide. 



This variety is easily distinguished by its compact form, sub-parallel branches, 

 the usually irregular character of the connecting processes, and the narrow 

 summits of the carinas. 



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



