278 Systematic Paleontology 



Occurrence. — Helderberg Formation, Keyser Member. Cash 

 Valley and other localities near Cumberland. Abundant. 



Collections. — Maryland Ceological Survey, U. S. Xational Museum. 



Family TREMATOPORIDAE 



Genus MONOTRYPA Nicholson 



Monotrypa spheric a (Hall) 

 Plate LII, Figs. 5-8 



Favosites sphericus Hall, 1883, Rept. State Geol. N. Y. for 1882, pi. vii, figs. 



1-12. 

 Favosites sphwricus Hall and Simpson, 1887, Pal. N. Y., vol. vi, p. 9, pi. vii, 



figs. 1-12; pi. viii, fig. S. 



Description. — Specimens i'rom the Xew Scotland beds at Dawson, 

 Maryland, were found upon a close examination to have all the characters 

 of this rather abundant form described by Hall as a species of Favosites. 



As shown on the accompanying plate, the zoarium is massive and is 

 made up of polygonal zocecia whose diameter range from .35 to .35 mm. 

 The surface exhibits well-marked maculas, .5 mm. in diameter, composed 

 of zocecia larger than usual. Mesopores wanting. Diaphrao'ms rather 

 numerous in the successive mature regions. 



Although a single series of mural pores was described by Hall as occurr- 

 ing on each face of the cell tubes, this error was corrected in the description 

 of the plates by the same author. The Maiyland specimens before us are 

 silicified and the minute internal structure has not yet been studied. 

 However, the species probably belongs to Monotrypa as indicated above. 



Occurrence. — Helderberg Formation, New Scotland Member. 

 Dawson. 



Collections. — Maryland Geological Survey, U. S. National ]\Iuseum. 



Monotrypa tabulata (Hall) 

 Plate L, Figs. 1-i 



Chwtetes ? tabulatus Hall, 1883, Rept. State Geol. N. Y. for 1882, pi. ix, figs. 



12-15. 

 Chwtetes {Ptychonema) tabulatus Hall and Simpson, 1887, Pal. N. Y., vol. vi, 



p. 14, pi. ix, figs. 12-15. 



Description. — Zoarium rounded or in hemispheric masses, 40 or more 

 mm. in diameter. Zooecia polygonal, 4 to 5 in 2 mm. ; walls thin, strongly 



