316 
Aug. F. Foerste 
elongated granules, if these granules always were present, but the 
problem is complicated by the failure of these granules to appear in 
relatively numerous other specimens, otherwise indistinguishable 
from this group. There is a tendency to regard these species as 
identical with Crania scabiosa, originally described from the Rich- 
mond, but the latter do not possess the radially elongated minute 
granules. I am inclined to regard the Eden group specimens with 
the minute radiately elongated granules as sufficiently distinct from 
Crania scabiosa when present in large numbers, in which case the 
chances of detecting the radiately elongated granules are very favor- 
able, but it is quite evident, from the material already examined, that 
these features can not be depended upon as diagnostic for all speci- 
mens, since in relatively numerous specimens they have not been 
found . Since the term Crania percarinata appears first in the publica- 
cation in which the three so-called species here discussed were de- 
scribed, this name might be used to include at least all of those 
specimens in which the radiately elongated minute granules can be 
detected. 
Crania socialis is known only attached to crinoid stems. On 
these supports the shells could not develop symmetrically. Growth 
in a direction transverse to the length of the crinoid stem was es- 
pecially restricted, but this retarded growth to a certain extent also 
in a direction parallel to the length of the crinoid stem. As a result, 
the shell of Crania socialis appears not only abnormally elongated 
but also abnormally thickened. The fact that the apex in some 
specimens appears near one end of the elongated shell, and in other 
specimens near the middle of one of the sides suggests that the 
elongation is due to the character of the support and has no specific 
value. It, therefore, appears to me to differ from those specimens 
of Crania percarinata and Crania parallela which have radiately- 
elongated granules only in features dependent upon the form of the 
support which they accidentally chose. 
Detailed description of the types are given on the following 
pages. 
26. Crania dyeri, Miller 
1875. Crania dyeri Miller, Cincinnati Quarterly Jour. Sci., 2, 13, Fig. 3 
The type of Crania dyeri is numbered 1758 in the Dyer collection 
at Harvard University. It is cited by Bassler, in his Bibliographic 
Index of American Ordovician and Silurian Fossils, only from the 
