i 62 
BULLETIN OF THE LABORATORIES 
ous sections believed to be destitute of tubercles. The branches are 
quite thin and flat, with sharp edges. 
Cells arranged in longitudinal series, about eight in a length of 2 
mm. and ten or eleven in the same distance in breadth. Two intersti- 
tial cells are found between the ends of the cells, becoming more numer- 
ous in the lateral series of cells, and entirely pervading the tissues of the 
edges of the branches, which as a consequence appear striated in worn 
specimens. The branches are usually narrower than those of the last 
species, eight to twelve series of cells occupying the branches in this 
species, whereas in that species twelve to fifteen series are usually 
found. 
The largest frond so far observed, evidently not an entire speci- 
men, was 65 mm. long, and 50 mm. broad. The branches vary from 
2.3 to 3.2 mm, and sometimes attain a thickness of 1.2 mm. 
Associated with these species are long, slender fronds, undivided, 
with the characteristic cells and interstitial cells of the group, the lat- 
ter pervading the edges of the frond. One specimen is 55 mm. long 
and 5 mm. broad. They are probably the broken off stipes of some 
of the species last described. That the species all form a closely allied 
group may readily be seen. 
Locality a 7 id position. Soldiers’ Home Quarries, Todd’s Fork, 
Fauver’s Quarry, Alien’s Quarry, Fair Haven, Clinton Group. ^ 
Genus PACHYDICTYA, Ulrich. 
Zoaria composed of thick, often irregularly branching fronds, with 
distinct, smooth, non-poriferous margins. The cell walls are distinct 
and regular, neatly enclosing the oval cells ; at their ends they are 
usually approximate, nearly but not quite touching, the cells being ar- 
ranged in longitudinal series ; laterally, however, they are always sep- 
arated from each other by two quite thick lamellae which are continu- 
ous between the cell rows, following up the contour of the cells, but 
separated along the middle by a curved or quite straight line, which 
sometimes is indistinct. Species of this genus are usually referred to 
Stictopora., but in that genus the cells are separated by a series of small 
spiniform tubuli. 
X. Pachydictya emaciata, sp. n. 
{Plate XV, Fig. 8; Plate XVH, Fig 8.) 
Frond not known in its entire state, only one specimen (and that 
