92 THE PALEONTOLOGY OF MINNESOTA. 
[Streptelasma. 
STREPTELASMA BREVE 1. sp. (Ulrich). 
Fig. 7, Streptelasma breve Ulrich, Galena limestone, near Fountain, Minnesota. a, an average speci- 
men, natural size; 6, an unusually straight example; c, the flattened but entire calyx of 
another specimen ; d, represents the greater part of the calyx of a fourth example, x 2, showing 
the central union and arrangement of the septa and fovex in a very clear manner. 
Corallum free, simple, conical, small, curved, expanding very rapidly, the width 
greater than the hight. An average specimen is about 11 mm. high and 16 mm. wide 
across the cup. In a small specimen the measurements are, respectively, 7 and 
11 mm. Surface marked with fine encircling lines and stronger annulations of 
growth ; occasionally also with delicate vertical ribs. The latter seem, however, to 
be restricted to the lower half of the corallum. * Calyx deeply concave, the bottom 
extending to a point a little beneath the middle of the hight. Septa large and 
small, the latter shown only in the extreme outer part of complete calices, the 
ormer extending to the center where they unite into four bundles of from six to 
eight in each. Principal septum straight, sometimes stronger than the others, 
extending to the center through a well marked fovea. The septa on each side of it 
arranged in a pinnate manner, uniting centrally. Lateral fovee narrow, but gen- 
erally recognizable. Opposite septum forming the central one of usually fifteen 
septa that are radially arranged in the half of the calyx on the shorter or concave 
side of the corallum. Asa rule it is distinguished by its greater strength and prom- 
inence. Lateral septa inconspicuous, shorter than the others. Total number of 
septa in a specimen of the average size about sixty-four, of which thirty-two are 
large and long, while an equal number belong to the intermediate rudimentary set. 
All of them seem to have been obscurely dentate, and but little elevated, so that 
they are to be termed ridge-shaped rather than lamellate. At the center of the 
calyx the septa inosculate, forming a limited number of cells bounded by spinulose 
walls. As shown in fig, 2d, the condition described is scarcely to be called a twist- 
ing of the septa, Internal structure unknown, 
