322 
Aug. F. Foerste 
the crinoid stem, but this evidently is due in part to compression 
parallel to the shorter axis of the shell. Only very obscure traces 
of elongated granules are noticed at one point along the margin 
of the shell. 
Another specimen of Crania socialis is numbered 8868 in the 
Faber collection at Chicago University. It consists of 17 larger 
and 10 considerably smaller shells attached to a crinoid stem 22 
mm. long and 3.5 mm. in diameter. At first sight this group of shells 
appears merely like numerous specimens of Crania scabiosa. Their 
surfaces are comparatively smooth, and there are traces of concentric 
striae, although these are not very conspicuous. On closer examina- 
. tion, however, very fine radiating lines are noticed, which apparently 
consist of irregularly arranged short striae directed in a radiating 
direction. These striae are preserved best along the younger parts 
of the shells, along the margin, the older, more central parts, being 
smooth. 
30. Crania albersi, Miller and Faber 
(Plate III, Figs 8 A, B) 
1891. Crania albersi, Miller and Faber, Jour. Cincinnati Soc. Nat. Hist., 17, p. 
151, Plate 8, Figs. 17-19 
The type of Crania albersi, No. 8863 in the Faber collection at 
Chicago University, consists of an upper valve resting upon a 
specimen of Zygospira modesta. The Crania evidently was not 
attached to the Zygospira during life, but the upper valve of the 
Crania had become loosened from its original area of attachment 
and had drifted to its present position, on top of the Zygospira, 
before becoming buried in the sea mud. Its original support must 
have been some shell with much narrower and less divergent mark- 
ings than the plications of Zygospira modesta, judging from the 
narrow, subparallel plications, approximately vertical to the pos- 
terior margin, which are shown by the type, and which evidently 
are superimposed upon the fine radiating striae characteristic of the 
species of Crania under discussion. The supporting shell may 
have been some species of Rafinesquina. The length of the type 
specimen is 4 mm. ; the width can not be determined with accuracy 
since the margin on the right side of the specimen is broken away 
for its entire length, but this width is estimated at 5.3 mm., and 
the height of the valve is about 1.5 mm. Along the margin of 
this type, the number of radiating striae varies from 6 to 8 in a width 
