184 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
Basals forming a small basin, which at the bottom is slightly excavated 
for the reception of the column. Radials and costals of nearly equal size, 
one third longer than wide, their lateral faces distinctly convex, so as to give 
to the sides a sort of scalloped appearance. Distichals free from the ninth 
or tenth plate; the four or five lower ones elongate, in form and size re- 
sembling the costals; the succeeding ones gradually decreasing in length; 
and the upper ones as short as the free arm plates. Arms ten, apparently 
short; composed of low cuneate pieces with somewhat rounded outer edges. 
The first pinnule starts from the second distichal; it is stronger than the 
others, and, like the three or four succeeding ones, incorporated into the 
calyx. The free pinnules are more slender and longer; they consist of six 
to seven joints, twice as long as wide. Interradial spaces deepening toward 
the middle, and deepest in their upper portions. They are composed of 
a very large number of minute pieces, are irregularly arranged, tuberculous 
and slightly stellate. Similar plates fill up the spaces between the distichals. 
Anal interradius wider; divided by a longitudinal row of fifteen or more 
large anal plates, which in form and size resemble the lower brachials, and 
their sides are scalloped in a similar manner. The row terminates in a small 
protuberance near the margin of the disk, which contains the anal opening. 
Ventral disk hemispherical, pentangular in outline, the surface slightly ele- 
vated in the direction of the food grooves; composed of hundreds of minute 
pieces; the ambulacra subtegminal. Column quadrangular, its sides dis- 
tinctly concave. Axial canal pentangular. 
Floyrizon and Locality. — Hudson River group; Warren Co., O. 
Types inthe collection of Mr. I. H. Harris of Waynesville, O. 
Remarks, — Among the specimens examined, there is a very interesting 
small one, in which the interradials do not touch the basals. In this speci- 
men it is most remarkable how the interradials vary in size. Three of them 
are tolerably large, but they are isolated from each other, and from the 
radials and basals, by numerous small, almost microscopic pieces, smaller 
than the corresponding plates in more mature specimens. The larger plates 
occupy approximately the position of the first and second row of inter- 
brachials in the Actinocrinidw, and undoubtedly represent them, being 
pushed out of position by the development and intercalation of supplemen- 
tary pieces. 
