224 PALEOZOIC PALEONTOLOGY. 
to be transversely corrugated. In cross-section the zoacia are 
polygonal in outline, about ten of average size occupying the space of 
3.5 mm. Interspersed with the average-sized zocecia are smaller ones 
which are younger, but no true mesopores are present. In longi- 
tudinal section the walls of the zoccia are wavy. Diaphrams are 
absent from the lower portion of the tubes, but are present distally, 
becoming more and more frequent toward the exterior, the outermost 
ones being about one tube diameter apart. 
Remarks.—This species most closely resembles Chetetes (Pagt 
nema) tabulatus H. & S., since referred to the genus Monotrypa by 
Nickles and Bassler, which is said to be derived “probably from the 
Upper Helderberg group, Schoharie, N. Y.,” so that its geologic 
horizon is somewhat uncertain. The transverse zocecial corrugations 
of M. tabulatus are more conspicuous than in the New Jersey species, 
and the diaphrams are apparently entirely absent. 
PTILODICTYA FRONDOSA Nn. sp. . 
Plate XIX., Figs. 1-4. 
Description.—Zoarium bifoliate, frondescent in form, often more or 
less undulate; beginning with a narrowly-rounded or obtusely-pointed 
base of attachment or articulation, from which point it broadens 
rapidly, the distal end more or less bluntly rounded; the axial line 
is curved gently near the base, becoming nearly straight beyond the 
first third of its length. The mesotheca, along which specimens almost 
unformily separate, is marked by concentric lines subparallel with the 
margins. The zocecia are arranged in parallel, longitudinal rows. In 
tangential section they are seen to be subelliptical in outline; the four 
or five axial rows are slightly smaller than the others, but are not 
sharply differentiated from them, with their longer axes directed 
parallel with the axis of the zoarium. On either side of these mediak 
rows the longer axes of the zoccial openings are slightly oblique, 
diverging outward at an angle of about 15°, while the zocecial open- 
ings themselves are arranged in diagonal rows, diverging at an angle 
of about 55° from the axis. In vertical section the zoccia are slightly 
curved and are crossed by numerous diaphragms, many of which are 
incomplete, situated at distances of from one-half to one tube diameter 
apart. 
Some of the larger zoaria attain a length of from 70 mm. to 80 
