170 Thirty-second Report on the State Museum. 



Dissepiments very slender, eight in the space of five mm., width from one 

 third to one-half that of the branches, not expanding at their junction with the 

 branches. 



Fenestrules subquadrangular, about twice as long as wide, width variable, but 

 averaging a little less than that of the branches. 



Cell-pores in two ranges, opening nearly directly upward ; apertures large, 

 circular, three in the space of a fenestrule, distance from each other equal to or 

 less than the diameter of an aperture ; margins distinctly elevated, but very 

 slightly indenting the border of the fenestrules, apparently granulose ; space 

 between the ranges of pores occupied by a low, rounded ridge, but slightly ele- 

 vated above the branch, and frequently a slight groove on each side of the ridge. 



Formation and locality. Lower Helderberg group, near Ciarksville, N. Y* 

 Fenestella Thyene, n. sp. 



(PLATE XXI, FIGS. 1-5.) 



Bryozoum broadly cup-shaped, undulating. Branches strong, nine in the space 

 of five mm. ; non-poriferous side angular or subangular, obscurely striated ; 

 bifurcations moderately distant, irregular. 



Dissepiments eight in the space of five mm., width slightly more than one- 

 half that of the branches, expanding at their junction with the branches ; on 

 non-poriferous side of frond angular, on poriferous side rounded. 



Fenestrules broadly oval or nearly round ; the angularity of the branches and 

 dissepiments on non-poriferous side give them an appearance more nearly circu- 

 lar than is really the case ; width nearly the same as that of the branches > 

 slightly longer than wide. 



Cell-pores in two ranges, opening obliquely outward ; cell-openings small, 

 round, three in the space of a fenestrule, counting those opposite the dissepi- 

 ment ; margins elevated ; space between the ranges of pores carinated, carina 

 comparatively thick, elevated, about two-thirds the thickness of the branch, ex- 

 panded above. 



A single specimen of this species shows, at a distance from the base, the long,, 

 oval fenestrules, and flattened, striated branches. 



This species, on the non-poriferous side, bears a close resemblance to F. 

 Coronis (plate xxi, figs. 10-13), but is distinguished from that species by its- 

 more compact mode of growth, more slender branches, and smaller fenestrules. 



Formation and locality. Lower Helderberg group, near Ciarksville, N. Y* 



Fenestella Idalia. 



(PLATE XXI, FIGS. 6-9.) 



Fenestella Idalia, Hall. Twenty-sixth Rep. N. Y. St. Mas. Nat. Hist., p. 95. 1874. 



Bryozoum cup-shaped. Branches moderately strong, closely arranged, eleven 

 in the space of five mm. ; on non-poriferous side rounded, striated, striae very 



