105 
in F. Java are from two to four times as large as those of F'. magnifica). From Polypora (Gor- 
gonia) ripisteria (Goldfuss), the present species is separated by its rectangular, not oval, fenes- 
trules, the much greater proportionate and absolute width of the fenestrules, and the straight, 
not flexuous, branches. 
I have only seen a single specimen of F. magnifica, and that only exhibits the reverse 
of the coeneecium ; but the general characters of the frond are so unlike any previously recorded 
species of Fenestella with which I am acquainted, that I have thought myself justified in 
forming a new species for its reception. 
Locality and Formation.—Corniferous Limestone of Port Colborne. 
128, FENESTELLA MARGINALIS (Nicholson). 
Polyzoary forming a fan-shaped expansion, of unknown dimensions. Branches straight, 
nearly parallel, about four in the space of two lines. Dissepiments exceedingly narrow, not 
more than one hundredth of an inch in width, slightly expanded at their points of junction 
with the branches, quite straight, and separated by intervals of one line, slightly alternating 
in contiguous rows. No cells upon the dissepiments. Fenestrules oblong, regularly rectan- 
gular, nearly twice as long as wide, (nearly one line in length and less than half a line in 
width) ; three fenestrules in a quarter of an inch measured vertically, and five in the same 
space measured transversely. Two marginal rows of large flask-shaped cells, between which 
are two or sometimes three rows of minute elongated cells, which probably occupied a central 
keel. Four large cells to a fenestrule, and one at the origin of each dissepiment. As in the 
case of the preceding species, I have only a single fragmentary example of this species, but its 
characters are so peculiar that I have no doubt as to its specific distinctness. Our specimen 
is one exhibiting the back of the polyzoary, but the outer striated non-celluliferous layer has 
been denuded, and the proximal ends of the cells are thus brought into view. 
In its general form /’. marginalis is clearly 
a genuine Fenestella, as shown by the straight 
branches, the distinct straight non-celluliferous 
dissepiments, its rectangular fenestrules, and its 
possession of a row of large cells on each side of 
each branch. This last character separates it from 
Polypora, and the others distinguish it from Rete- 
pora. The specimen does not enable one to affirm 
with certainty that the two lateral rows of cells 
were separated by a median keel, but it appears 
highly probable that this was the case. In the 
Fig. 42. genus or sub-genus Fenestrellina (D’Orbigny), the 
Fenestella marginalis (Nich). a. A fragment, natu- mesial keel separating the two lateral rows of large 
ral sige; b, Aertonof the sume maghided . A'vorton cells, carries a central row of minute cells, Tn 
and showing the large marginal cells and the minute IB: marginalis, however, the space between the 
central cells. From the ernitenons Limestone. lateral rows of cells carries a series of minute 
closely-crowded cells, which are arranged in general in two alternating rows, but sometimes 
in three. This character, so far as I am aware, has not hitherto been observed in any 
species of Fenestella except F. rigidula (McCoy), and it may, perhaps, afford a ground of sub- 
generic distinction. If, as is most probable, a median keel were present, it must have ex- 
hibited the openings of two or three rows of minute cells. 
In its general form, F. marginalis exhibits some resemblance to F. magnifica (Nich.), but 
its dimensions are much smaller. The former has four branches in a space of two lines, and 
five fenestrules in a quarter of an inch measured transversely, whilst the dissepiments are 
exceedingly thin, and the length of the fenestrulesis nearly double the width. On the other 
hand, in F. magnifica there are three branches in a space of two lines, and about three fenes- 
trules in a quarter of an inch measured diagonally or transversely, whilst the dissepi- 
ments are about as thick as the branches, and the fenestrules are only slightly longer than 
wide. 
Locality and Formation.—Corniferous Limestone, Port Colborne. 
