8o 
BULLETIN OF THE LABORATORIES 
King, is distinguished by the absence of dimorphic pores, and the pres- 
ence of more than two rows of cells. 
VII. Septopora biserialis, var. gracilis, Meek. 
(PlateKll, Fig. 7, a, b, c.) 
Synocladia biserialis (gracilis, suggested), Meek, Ohio Pal. Vol II, p. 326. 
Zoarium flabellate, composed of three or four strong radiating 
stems, forming a net-work by pinnate division, and the union of oppo- 
site, short, lateral branches. Intercalated stems, arising from the co- 
alescing of lateral branches, are not unfrequent. All stems increase 
in size above. Lateral branches short, inclining at angles of 60 de- 
grees or more to the stems, those of adjacent stems uniting, the union 
rounded, angular, nodose, or slightly produced. Poriferous face with 
two rows of cells ; alternating with these, usually nearer the margin, 
although sometimes between the cells, are pores of about one-third the 
size of the cells. The median ridge is narrow, distinctly nodose, 
nodes not quite as numerous as the cells on either side. Non-celluliferous 
face, with the sides sloping from a convex median ridge, which some- 
times is indistinct, longitudinally striated, striations strongest along the 
median area. Dimorphic pores very small, situated singly or in pairs 
at the junction of the branches with the stems, occasionally a few oth- 
ers scattered about in various positions, but not with the frequency or 
irregularity indicated by Meek in his figures of A. biserialis from the 
Coal Measures of the West. • 
‘ From Septapora biserialis. Swallow, this form may be distinguished 
by the tendency towards the formation of a median ridge on the non- 
poriferoLis side, by the regularity of arrangement of most of the dimor- 
phic pores, both on the celluliferous and non-celluliferous sides, and 
by the more distant stems and branches, forming larger fenestrules. 
A. Cestriensis, Front, referred by E. O. Ulrich to A. biserialis as a va- 
riety, differs from our form in wanting the dimorphic pores on the cel- 
luliferoiis side, or at any rate in having them much less numerous. 
Ulrich’s studies indicate great variability in this species, and our form 
would give it also wide geographical distribution. 
'The measurements in this case are variable and scarcely specific, 
but a few may here be given of a specimen considered typical. 
About 8 stems occur in a width of 10 mm ; 9 branches occur in the 
same length. From the Feiiestellidce this species will of course be at 
