106 
129. FENESTELLA CRIBROSA (Hail). 
Fenestella cribrosa (Hall), Pal. N. Y., Vol. IL., p. 166, Pl. XL., figs. 3a, 30. 
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 io 
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 
of the celluliferous side are also sufficiently distinctive. Some 
examples exhibit proportions slightly larger than those given 
: in the above description, and these may possibly constitute a 
Fig. 43, distinct variety or even a distinct species. é 
a Fragment of the non-celluliferous Locality and Formation.—Not uncommon in the Hamil- 
side of Fenestella cribrosa (Hall), en- ton Group at Widder, and at Bartlett’s Mills, near Arkona, 
larged ; 6 fragment of the celluliferous : 
side of the same enlarged. From the Township of Bosanquet. 
Hamilton Group. 
130. FENESTELLA TENUICEPS (Hall). 
Fenestella prisca (?) (Hall), Pal. N. Y., Vol. IL. p. 50, Pl. XTX., Fig. 4, a—m. 
Fenestella tenwiceps (Hall), Pal. N. Y., Vol. II. p. 165, Pl. 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, trom the Clinton and 
Niagara Formations of the State of New York. Though seve- 
ral of our specimens, by decortication 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- 
Fig. 44. 
Fenestella tenwiceps (Hall = : : 
ment of the natural size - ee a ec cording to Hall, however, the branches are strongly carinate on 
Saine enlarged. From the Corniferous this aspect, with a sharp-edged keel, and the cells open on the 
Limestone. - 
sides of the branches. 
