SILURIAN FAUNAS. 225 
mm., with a width of 30 mm., but usually they are relatively some- 
what narrower. About four zowcia oceupy the space of 1 mm. longi- 
tudinally and about four and one-half transversely. 
Remarks.—This species resembles P. expansa Hall, but is curved 
and does not have the perfectly parallel margins of that species; it 
also lacks the axial rows of zocecia, which are conspicuously narrower 
than those on the sides. In form the zoarium is almost identical with 
Phenopora platyphylla Jas., but thin sections show the two forms to 
be generically distinct. The species is apparently most closely allied 
to that called Ptilodictya lanceolata var. americana by Feerste, but it 
does not have the sharply differentiated medial rows of smaller zooecia 
which seem to be indicated in the illustrations of that species, and 
the basal portion of the zoarium is more curved. In none of the 
- New Jersey specimens has the cell-bearing surface been seen clear of 
the matrix, so that it is not possible to state with certainty whether 
or not monticules are present, but they seem to be absent. 
(e ESCHAROPORA SILUBIANA Nl. Sp. 
Plate XVIII., Figs. 6-7. Plate XIX., Figs. 8-9. 
Description.—Zoarium thin, bifoliate, complete outline unknown. 
The mesothecal surface, along which the specimens uniformly sepa- 
rate, is uneven, with numerous, more or less irregular, curved, trans- 
verse wrinkles. In tangential section the zocecia are more or less 
irregularly hexagonal in outline, the openings being subelliptical. 
The prostrate portions of the zocecia are elongate and are initially 
arranged in longitudinal series, but when they become erect adjacent 
series are crowded together, giving to the apertures an irregularly 
decussate arrangement. In vertical section the zocecia are thick walled 
above and in their erect portions usually about four slightly-convex 
diaphragms are present. The two hemisepta have been clearly seen 
in but one zocecium, though it is possible that they may usually be 
present. 
Remarks.—This genus has not before been recorded from strata 
younger than the Ordovician. ‘These specimens, however, agree essen- 
tially in all generic characters with the Ordovician forms, but the 
zoaria are apparently larger and more irregular in form than is 
usually the case in the older species. 
15 
