OF DENISON UNIVERSITY. 
157 
rows, the description is intelligible and pertinent ; if not, it has no tan- 
gible meaning for either species. We believe that in this case, where 
we have two generic references, a description including characteristics 
of two species, and figures of two species, it is most advisable to make 
the original description the material from which to unravel the form 
which is to be considered authentic. 
Locality and position. Forms with parallel sides are found frequent- 
ly at Todd’s Fork, Clinton county, and rarely at the Soldiers’ Home 
Quarries. Broader forms with less regular sides are common at the 
Soldiers’ Home Quarries. Clinton Group. 
Genus PH^NOPORA, Hall. 
Zoaria forming simple or branching fronds without a distinct non- 
poriferous edge ; the pores of the edge seem to be of the same rank 
with the interstitial cells. Cells arranged in longitudinal series, sepa- 
rated at their ends typically by two interstitial cells, although their num- 
ber may be so increased in different parts of the same frond as to even 
completely surround the cells. A transverse septum at the base of the 
cells is also characteristic. The bases of the zoaria are attenuated and 
rounded, or somewhat pointed, showing that articulation had formerly 
existed with some fixed base. 
VI. Ph^nopora platyphylla, fajnes. 
{Plate XVI, Fig. i ; Plate XVH, Fig 6 .) 
Phaenopora (Ptilodictya) expansa, pars. Hall and Whitfield, including Plate 
V, fig. I. 
Ptilodictya platyphylla, James, 1879, Paleontologist. No. 3. 
Ptilodictya bipunctata (Van C!eve) Hall, 1883. 12th Indiana Geol. Report. 
Frond beginning with a small, narrow stipe, which at its origin is 
obtusely pointed, or almost rounded, indicating articulation with some 
attached base, rapidly widening above into a broad fiabellate expan- 
sion, the contour in general being rounded, but flexuous in certain places 
where growth has been irregular; never branched. The surface cov- 
ered by conspicuous, rounded tubercles, having a tendency to arrange 
themselves in rows, about six tubercles appearing in a length of 15 
mm ; sometimes the tubercles have a tendency to be somewhat point- 
ed. The surface is occupied by the cell mouths, which are very small. 
