Fauna of the Morrow Group 
167 
Pustula globosa n. sp. 
Plate X, figures 7-9. 
Description. Shell small, sub-globular in shape, usually a 
little wider than long, length of hinge-line less than the greatest 
width of valve. Dimensions of the type specimen are : greatest 
width, 8.1 mm. ; length of hinge-line, 6.7 mm. ; length from hinge- 
line to anterior margin, 7.6 mm. ; convexity of pedicle valve, 
±5.5 mm.; length from umbonal region to anterior margin, 
9.0 mm. 
Pedicle valve strongly and regularly convex longitudinally and 
transversely, sub-hemispherical in shape, the venter slightly 
flattened in old age ; beak small and pointed, incurved over hinge- 
line ; ears small and poorly defined, cardinal extremities rounded. 
Surface of valve non-costate, crossed by faint concentric lines 
of growth which near the margin in the older individuals become 
stronger and more conspicuous ; a few bases of large erect spines 
scattered irregularly over the surface, about as numerous in the 
visceral portion of the valve as near the margins. 
Brachial valve concave, the surface sloping rather abruptly 
from the umbonal region toward the ears which are more sharply 
defined than in the pedicle valve, somewhat flattened in the 
visceral region but deflected strongly downward toward the 
lateral and anterior margins; beak small and inconspicuous* 
umbonal region moderately well developed. Surface ornamen- 
tation similar to that of the pedicle valve with the concentric 
lines perhaps somewhat more conspicuous. 
Remarks. This rather abundant form may be compared with 
P. indianensis (Hall) of the Salem limestone which it resembles 
in a general way. It differs from that species in its somewhat 
larger size and more spherical shape, its greater breadth through 
the visceral region and more nearly parallel main flanks. There 
seems to be no Pennsylvanian form with which it is comparable. 
The reference to Pustula is made on account of the absence of 
costae and because it is “essentially spinose in ornamentation.'^ 
It will probably be advantageous to separate such non-costate 
forms with comparatively large erect spines from the typical 
“pustulose" members of that genus and designate them by some 
other generic name. In this instance it is recognized that there 
is a possibility that this form may in reality be a Produclella 
