RHINIDICTYONIDJE. 57 
thin section prepared from the type specimen, figured, on PI. XX, indicates. The zooecia are 
large, 5 to 6 in 2 mm., measuring longitudinally and about 10 in the same space transversely. 
Occurrence. — Rare in the shales at Lockport, N. Y. 
Family STICTOPORELLIDJE INioltles arid. Bassler. 
Genus T^NIODICTYA Ulrich. 
Zoarium growing from a basal expansion into narrow, dichotomously divided branches 
or broad fronds; zooecial structure much as in Ptilodictya. The species described below, 
although the earliest known, appears to possess all the essential generic characters. 
T-3ENIODICTYA SCHUCHERTI II. sj). 
PI. XX VI I, figs. 10-13. 
Zoarium, as observed from the only specimen found, of flexuous, parallel-edged branches, 
3 mm. in width, dividing dichotomously at intervals of from 6 to mm. Zooecial apertures 
rather large for the genus, 4 in 2 mm., measuring longitudinally, and 7 in the same space 
transversely, arranged in longitudinal series. 
The figures of the internal structure show that this form has all the characters of Tb. nio- 
dictija with the exception that the interspaces are not transversely lined as in other species 
of the genus. This feature is one of age and its absence in the specimen studied may be 
due to its youthful condition. 
The large zooecia will distinguish this from other species of th genus. The only asso- 
ciated species with which it might be confused is Pachydictya crassa, but the oval aperture 
with thick ringlike walls and different internal structure 1 of the latter are points of difference. 
The specific name is in honor of Prof. Charles Schuchert, who collected the type specimen 
and to whom the writer is indebted for many favors. 
Occurrence. — Rochester shal ■, Grimsby, Ontario. 
Catalogue number, 35772, IT. S. National Museum. 
Family KIIINIDICTYOMD.P] TTli-ieli. 
Genus PACHYDICTYA Ulrich. 
The species of this genus found in the Rochester shale is a cosmopolitan form which has 
been noted in most of th ■ divisions of the Niagara. It is, therefore, of little value for pur- 
poses of exact correlation and marks the rocks of this group in general only. 
Pachydictya crassa (Hall). 
!']. Will, figs. 11, 12; PI. XXI. tigs. 14-16. 
Stictopora crassa Hall, Nat. Hist. New York, Pal. II, 1852, p. 45, pi. 18, figs. 4 a c. 
Ptilodictya crassa Nicholson and Hindi'. Canadian Journal, new ser., XIV, 1874. 
Stictopora scitula Hall and Simpson, Nat. Hist. New York, Pal. VI, 1887, pi. 61, figs. 24, 25. 
i Pachydictya scitula Ulrich, Geol. and Nat. Hist. Survey Minnesota, Final Kept., Ill, pt. 1, 1893, p. 147. 
The external features of this species have been well figured by Hall and Simpson and 
there is no difficulty in the identification of the form. 
Th A zoarium consists of a narrow, dichotomously branching frond with sharp, parallel 
edges; branches elliptical in cross set ion with narrow noncelluliferous margins marked 
by faint striae; zooecial apertures oval, arranged in parallel longitudinal rows separated by 
linear ridges, 4 in 2 mm. measuring lengthwise. 
The narrow bifoliate branches with large, rounded zooecia distinguish the species from 
all associated forms. 
Occurrence. — Common at all the Rochester shale localities in New York and Ontario; 
also very abundant in the Osgood beds at Osgood, Ind., as well as in the Niagaran rocks 
'in general. 
Catalogue numbers, 35754, 35755, U. S. National Museum. 
