106 



Fj 43 

 a Fragment of the non-ceiiuiiferous 



129. FENESTELLA CRIBROSA (Hail). 



Fenestella cribrosa (Hall), Pal. N. Y., Vol. II., p. 166, PI. XL., figs. 3a, 36. 

 Polyzoary forming a flattened expansion of unknown dimensions. Branches strong, par- 

 allel, often undivided for a distance of half an inch or more, very closely approximated, fifteen 

 or eighteen in a quarter of an inch. Dissepiments about the same width as the branches, or 

 slightly narrower, not dilated at their points of junction with the branches. Fenestrules oppo- 

 site, sub-alternate, or alternate in contiguous rows, oval or quadrangular, one-third longer 

 than wide. From ten to twelve fenestrules in a quarter of an inch measured vertically, and 

 from fifteen to eighteen in the same space measured transversely. Non-poriferous side closely 

 and finely granulated and striated. On the poriferous side, both the branches and the dis- 

 sepiments are keeled with a prominent and very sharp carina, and the dissepiments are placed 

 upon a lower plane than the branches, so that in many cases the latter alone are visible. Two 

 rows of cellules on each branch, opening by comparatively large rounded apertures on the lateral 

 aspects of the branch. No pores on the mesial keel or on the dissepiments. Two pores to 

 the length of a fenestrule, and one opposite the base of each dissepiment. 



I have no doubt as to the identity of our specimens with Fenestella cribrosa (Hall), from 

 the Niagara Limestone, though Hall's description embraces only the non-celluliferous side. 



The species is quite readily distinguished from all other 

 known species of the genus by the approximation of the slender 

 branches and dissepiments, from which it results that an ex- 

 traordinarily large number of fenestrules occupy a given space, 

 whether measured vertically or transversely. The characters 

 "' the celluliferous s '^ ;ir> ' a ' s " sufficiently distinctive. Some 

 cxam pl es ex bibit proportions slightly larger than those given 

 in the above description, and these may possibly constitute a 

 distinct variety or even a distinct species. 



Locality and Formation. Not uncommon in the Hamil- 

 side of Fenestella cribrosa (\\a\\), en- ton Group at Widder, and at Bartlett's Mills, near Arkona 



larged ; b fragment of the celluliferous m i r> T> 



side of the same enlarged. From the -LOWnsnip 01 UOSanquet. 



Hamilton Group. 



130. FENESTELLA TENUICEPS (Hall). 



Fenestella priscaf?) (Hall), Pal. N. Y., Vol. II. p. 50, PL XIX., Fig. 4, a-m. 

 Fenestella tenuiceps (Hall), Pal. N. Y., Vol. II. p. 165, PI. XL. D, Fig. 2, a-h. 

 Polyzoary infundibuliform or forming a flattened expansion of a fan-shaped figure. 

 Branches nearly straight, sub-parallel, increasing by bifurcation, which usually takes place at 

 intervals of two or three lines, though sometimes the branches remain undivided for half an 

 inch or more. From eight to ten branches in the space of one quarter of an inch. Dissepi- 

 ments slightly narrower than the branches, markedly expanded at both ends, and separated 

 by intervals of a third of a line or rather more. Fenestrules oval, not distinctly rectangular, 

 nearly or quite twice as long as wide, about six or seven in a quarter of an inch, measured 

 vertically, and from eight to ten in the same space measured transversely, sub-alternate or 

 alternate in contiguous rows. Non-celluliferous surface, finely striated. Cells in a double row 

 on each branch, about four to each fenestrule. 



Specimens conforming to the above characters are of 

 common occurrence in both the Corniferous Limestone and the 

 Hamilton Formation of Western Ontario, and little doubt can 

 be entertained as to their identity with the species described 

 by Hall under the name of F. tenuiceps, from the Clinton and 

 Niagara Formations of the State of New York. Though seve- 

 ral of our sp3chnens, by decor tication of the non-poriferous 

 layer, show the proximal ends of the biserial cells, none of them 

 actually exhibit the celluliferous face of the polyzoary. Ac- 

 cording to Hall, however, the branches are strongly carinate on 

 same enlarged. From the Corniferous this aspect, with a sharp-ed^ed keel, and the cells open on the 



Limestone. , ' , 



sides of the branches. 



