52 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
A permanent fixation of the Crinoids would perhaps restrict the geo- 
graphical range of the species, whereas we know that some of them have 
a very wide range. A majority of the species from the Lower Burlington 
group at Burlington are found almost unaltered in the southwestern part of 
New Mexico, and some in Arizona, and many species of the Keokuk group 
have been traced from southern Iowa as far down as Alabama. And we find 
in Scotland and eastern Russia, with but slight modifications, the same forms 
which flourished in the Mississippi Valley during the epoch of the Kaskaskia 
group. 
B. Basals and Infrabasais. 
The base of a Crinoid consists either of one or two rings of plates, to 
which the terms “ basals” and “infrabasals” are applied. In dicyclic forms, 
the infrabasals constitute the proximal ring of the calyx; the basals the next 
circlet above. The former are radially disposed, the latter interradially. 
The plates of either ring are in contact laterally, except the basals in a few 
species of Zeacrinus and Calpioerinus, where the truncated lower angles of the 
radials, and occasionally the radianal, reach down to the infrabasals. The 
basals are followed directly by the radials, except in the Acrocrinide, in 
which they are separated from the latter by a belt of auxiliary pieces, which 
occupy a large part of the dorsal cup. 
The term “basals’’ was applied by the earlier writers invariably to the 
proximal ring of the calyx, and when there were two rings, the plates of the 
upper one were called “subradials” by some authors, while others called them 
“ parabasalia.” To Dr. P. H. Carpenter* belongs the credit of having been 
the first to point out that in dicyclie Crinoids the so-called ‘“ subradials”” — 
and not the proximal ring — are the homologues of the basals in the mono- 
cyclic base, and that the lower ring in the dicyclic forms is an additional 
element in the calyx. He demonstrated that from a morphological point of 
view the same set of plates cannot be interradial in one genus, and radial in 
another, and he considered the basals, which alternate with the radials, to be 
the representatives of the genitals in the Urechins. The force of his argu- 
ment has been generally acknowledged, and the American authors writing 
since 1879 have adopted Carpenter’s method, with the exception of 8. A. 
Miller, who still clings tenaciously to the old terms. Carpenter called the 
plates of the proximal ring “ under-basals,” for which the term “ infrabasals” 
* “Oral and Apical Systems of Echinoderms.”’ Quarterly Journ. of Microscop. Sci., Vol. VIIT., 
pp: 351-383, 
