REPORT ON THE CRINOIDEA. 61 
which they now possess. - There are no true pinnules in Cyathocrinus proper, but only 
repeatedly branching arms, which must therefore have contained the genital glands; and 
each of the branches borne by one of the lower axillaries may fork again several times, so 
that they cannot be compared to the long, undivided pinnules of Hyocrinus (Pl. VL. 
figs. 1, 2). In Poterioerinus, on the other hand, the successive arm-joints bear pinnules 
which are not specially different from those of Neocrinoids ; while the mode of branching 
of the arms resembles that characteristic of Pentacrinus miilleri, and more especially of 
Extracrinus, the axillaries being generally limited to the outer arms of the ray, and 
having unequal distal faces." 
It is in the curious genus Barycrinus, which was separated from Cyathocrinus by Mr. 
Wachsmuth, that we find the nearest approach to the pinnule-arrangement of /Tyocrinus. 
According to Wachsmuth and Springer” “all the main arms, instead of bifureating, 
give off at regular intervals, alternately on opposite sides, and from the inner margins of 
the plates, short, rounded, simple armlets, which in most species throw off secondary 
branches as in Botryocrinus, and these armlets here as there, probably performed the 
office of pinnule.” Barycrinus hoveyi, var herculeus, M. and W., is one of the excep- 
tional species in which the armlets are simple and without secondary branches. The 
excellent figure of it which is given by Meek and Worthen® shows these armlets 
to come off alternately on opposite sides just as in Hyocrinus, but from every second 
joint, instead of from every third (Pl. VI. figs. 1, 2). They have unfortunately never 
been found in a perfect condition; and we cannot tell therefore whether they reached 
to the level of the top of the arms proper as in Hyocrinus, though Meek and Worthen’s 
description seems to indicate that such is the case. 
The difference between these armlets of Barycrinus herculeus and those of Hxtra- 
erinus is that the former seem to bear no pinnules as the latter do, and must therefore 
have contained the genital glands ; while they come off alternately from opposite sides of 
the main arm-tfunk, and not from its inner one only as in Hxtracrinus. 
We have seen that the pinnule of a Neocrinoid is practically a reduced copy of an 
arm, but modified by the great development of the fertile portion of the genital gland 
which it contains, that part of the gland which is confined to the arm being usually 
sterile and known as the “ genital cord” or “rachis” (Pl. Ve. fig. 1; Pl. VIIla. figs. 4, 5; 
Pl. LX. fig. 6—ge.). 
Although it would seem improbable that the pinnules of Palzocrinoids are essentially 
different in nature from those of the Neocrinoids, Messrs. Wachsmuth and Springer 
have attempted to show that the small alternating plates covering the brachial ambu- 
lacra of Cyathocrinus are homologous with the pimnules of the Actinocrinide and 
Platycrinide. These are long, comparatively slender, and closely arranged side by side 
1 See p. 277. 2 Revision, part i. p. 103. 
3 Paleontology of Illinois, vol. v. pl. xiii. fig. 2. 
