Corals and Bryozoans of the Lower Helderbkro. 167 



tively distant, irregular ; from seven to nine branches in the space of five mm. ; 

 on non-poriferous side rounded, striated ; striae fine, distinct ; from three to 

 seven on a branch. 



Dissepiments slender, frequently oblique to the branch ; four in the space of 

 six mm., expanding at their junction with the branches, the expansion extend- 

 ing but a very slight distance from the branches. 



Fenestrules subquadrangular ; width varying from equal to two or three times 

 that of the branches. 



Cell-pores in two and three ranges ; the central range opens directly upward, 

 the two outer ranges nearly directly outward ; cell-openings oval, five in the 

 space of a fenestrule ; distance from each other less than the diameter of an 

 opening ; margins scarcely elevated ; at the junction of a dissepiment and branch 

 there is frequently a cell-opening on the expanded portion of the dissepiment. 



This species has, in some respects, very much the appearance of F. crebripora, 



but is of a much coarser growth, differing also in the number of ranges of pores. 



Formation and locality. Lower Helderberg group, Albany county, N. Y. 



Fenestella crebripora. 



(PLATE XX, ITGS. 1-3.) 



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



Bryozouni, form unknown — this species having been seen only in fragments. 

 Branches slender, distant ; eight in the space of five mm. ; on non-poriferous 

 side rounded, striated, striae fine, indistinct ; bifurcations moderately distant. 



Dissepiments very slender, oblique to the branches, six in the space of five mm. 



Fenestrules subquadrangular ; width from once and one-half to twice that of 

 the branches, length frequently double the width. 



Cell-pores in two ranges, large, oval, distance from each other less than their 

 diameter, four in the space of a fenestrule, opening outward obliquely to the axis 

 of the branch ; margins not elevated ; at the junction of the dissepiment with 

 the branch, there is frequently a triangular cell-pore in the expanded portion of 

 the dissepiment, opening directly upward ; space between cell-apertures not 

 carinated, though sometimes angular ; finely striated ; dissepiments also striated. 



Formation and locality. Lower Helderberg group, Albany county, N. Y. 



Fenestella Sylvia. 



(PLATE XX, FIGS. 4-7.) 



Fenestella Sylvia, Hall. Twenty-sixth Rep. N. Y. St. Mils. Nat. Hist., p. 86. 1874. 



Bryozoum large, funnel-shaped, rapidly spreading and radiatingly undulating. 

 Branches very slender, closely arranged, twelve in the space of five mm. ; non- 

 poriferous side rounded, striated, striae distinct, from three to five on a branch ; 

 sometimes the central striation is so large as to give a carinated appearance to 

 the branch ; bifurcations distant. 



