482 ATELECRINUS. 
the centrodorsal. First radials more arched, oblong, and quite free laterally, their breadth in the 
adult being one and a half times their length. Axillaries pentagonal, sometimes twice the length — 
of the second radials, into which they have a slight backward projection. Their width is about — 
equal to their length, but their proportions and also those of the second radials vary slightly in 
different individuals. : 
“First brachials well separated laterally, with their inner sides shorter than the more round ¥ 
outer ones. 
“Second brachials irregularly quadrate, projecting slightly backwards into the first. The fol- 
lowing joints have oblique ends and markedly unequal sides. Except in the syzygial joints, the 
length is at first less than the breadth, but gradually becomes more equal, and exceeds it after the 
fifteenth joint. Terminal joints rela- 
tively longer and more equal sided. — 
Arm bases smooth, but the middle 
and later joints overlap slightly. 
“The first syzygium in the third 
brachial. The following syzygies at 
intervals of from one to six, usually 
of two or three joints. 
“First pinnule nearly always on 
the twelfth brachial, and consisting 
of about a dozen elongated joints. 
The following ones increase in size 
and in the number of joints, de- 
creasing again towards the arm ends. 
The lower joints of the middle and 
later pinnules bear irregular spinous 
processes on their dorsal edges. 
“Mouth somewhat eccentric and 
surrounded by a large peristome. 
A little way behind this is the anal 
tube, which is also slightly eccentric 
in position. Disk 6mm. in diame- 
ter. In the “Challenger” specimen a 
very few minute calcareous granules 
are visible on its ventral surface, and 
also on its sides between the rays. 
Fia. 15. A. balanoides P. H. Carp. (nach Carpenter, 1. ec. “ 9 : 
1881, pl. 1): @ Seitenansicht des Calyx eines anderen — q ae trsahie a baleen 
“‘Blake’’-Exemplares als des auf unserer Tafel 6, Figur 5, ed. € brac am 
dargestellten X 8; 6, b’. Ein einzelnes Basale (ohne seine Close down upon and between the 
centralen Fortsiitze), b von der Aussenseite, b’ von oben X muscular bundles, and have a few 
14; c Radialia und Basalia von unten; die kleinen Fort- scattered sacculi at their sides. Color 
siitze an den Centralenden der Basalia sind fortgelassen of skeleton white or brownish white.” 
X 10; d das Centrodorsale von oben X 10. “The distinctive characters of 
Atelecrinus balanoides are: (1) the 
transversely oblong shape of the second radials, which are but slightly incised to receive the bluntly 
angular proximal edges of the axillaries; and (2) the outline of the lower part of the calyx, 
which slopes uniformly downwards from the radials on to the centrodorsal, without the basal — 
being specially prominent at the interradial angles as they are in Atelecrinus cubensis.” 
“The nine individuals of Atelecrinus which I have examined, all agree very well in their gen- _ 
eral characters, but differ considerably in the relative proportions of the two outer radials and of — 
the lowest brachials respectively. In all of them which have enough of the arms preserved, the 
first pinnule is on the twelfth brachial, except in one arm of one individual, in which the tenth — 
joint bears the first pinnule.” 
Ueber das Centrodorsale schreibt Carpenter 1881, 1. ¢., p. 67: 
“The acorn shaped centrodorsal of Atelecrinus balanoides is nearly as deep as high. 
opening of its cavity has a narrow pentagonal rim, from the interradial angles of which stro 
ridges descend the sloping walls, diminishing in size as they approach the apex, where they di 
