DEVONIAN FAUNAS. 343 
MOLLUSCOIDEA. 
BRYOZOA. 
FENESTELLA? sp. undet. 
Fragments of a fenestelloid bryozoan, too poorly preserved for 
identification, are not infrequently observed in the basal portion of 
the Oriskany, associated with the Orbiculoidea jervensis fauna. 
BRACHIOPODA. 
ORBICULOIDEA JERVENSIS Barrett. 
Plate XLY., Figs. 7-8. 
1878. Discina jervensis Barrett, Ann. N. Y. Acad. Sci., vol. I., p. 121. 
Description.—Shell broadly suboval or nearly elliptical in outline. 
Pedicle valve depressed-convex posteriorly and nearly flat anteriorly 
and laterally, or nearly flat throughout; the apex a little more than 
one-third. the distance from the posterior margin. Internally a promi- 
nent, rounded elevation extends from the apex more than half way 
to the posterior margin, growing narrower posteriorly, with the in- 
ternal pedicle opening at its posterior extremity. This interior eleva- 
tion represents the external pedicle groove. Brachial valve depressed- 
convex, its apex opposite that of the pedicle valve; the surface usually 
slightly concave from the apex to the posterior margin and convex to 
the anterior margin. Surface of both valves marked externally by 
fine, concentric lines of growth, and internally by indefinite, radiating 
lines, as well as by concentric markings. 
The dimensions of an average specimen are: length, 19 mm.; width, 
1? mm. 
Remarks.—This species occurs abundantly in the basal portion of 
the Oriskany, in the zone immediately following the trilobite bed. 
The zone characterized by this species is a well-marked one, and has 
