36 THE VOYAGE OF H.M.S. CHALLENGER. 
there is a complete ring of united basals as in the recent genera Atelecrinus and 
Thaumatocrinus (Pl. LVI. figs. 1-4). In the four other genera of recent Comatulidee, 
however, the primary embryonic basals undergo transformation into the well-known 
rosette, which is really a secondary structure. It lies over the chambered organ, between 
the under surface of the radial pentagon and the, upper face of the centro-dorsal ; but 
it is entirely concealed, and does not appear at all upon the exterior of the calyx. 
In many Comatulez more or less prismatic rods proceed outwards from the inter- 
radial angles of the rosette, and their ends are often visible on the exterior of the 
calyx. They occupy exactly the same positions as the rod-like basals of many fossil 
Comatulz, but do not represent them morphologically, for they are not developed from 
the primary embryonic basals. These last become transformed into the rosette, which 
is a secondary structure as shown by Dr. Carpenter ;' while the tertiary basals which 
are connected with its interradial angles are merely ossifications in the connective 
tissue of the synostosis between the radials and the centro-dorsal, and are somewhat 
variable in their development.” They do not occur in Antedon rosacea, nor in the 
species on both sides of the Atlantic which are most nearly allied to it, viz., Autedon 
phalangium, Antedon dentata, Antedon hageni, &c.; and they seem to be absent in 
Eudiocrinus, at any rate in Hudiocrinus semperi. But they reach a relatively large 
size in many tropical species both of Antedon and of Actinometra, in which latter 
genus I have never found them to be absent, and they also occur in Promachocrinus 
see fig. 1, A on p. 37). [See Note B. 
s p 
B. Tue RaApImALs. 
There is considerable variation in the degree of lateral union between the individual 
basals and radials of stalked Crinoids. Those of Holopus (Pls. I-IV.) are so intimately 
fused that the sutures are entirely invisible on the exterior of the tubular calyx. In 
Hyocrinus (Pl. VI.) the interradial sutures are quite evident, but those between the 
basals are very obscure. In Rhizocrinus, and especially in Rhizocrinus lofotensis, the 
sutures between the basals are usually entirely invisible, not only externally but also 
in transverse sections of the decalcified calyx; while the basiradial and interradial 
sutures are merely indicated by very faint lines on the surface of the cup (Pl. IX. 
figs. 1, 2); and strong measures are necessary before the individual jomts will separate 
from one another. In the Pentacrinide and Comatulide the union between the radials 
is less close and the sutures well defined, while the condition of the basals varies accord- 
ing to circumstances (Pl. XIII. fig. 1; Pl. XV. figs. 1,2; Pl. XVI.; Pl. XX. ; Pl. XXXIIT. 
figs. 8-10; Pls. XXXV.-XXXVII.; Pl. XXXIX.; Pl XLIII.). The union of the 
1 Phil. Trans., 1866, pp. 744, 745. 
2 The genus Actinometra, Trans. Linn. Soc. Lond. (Zool.), vol. ii. pp. 98-105 ; and the genus Solanocrinus, Journ. 
Linn. Soc. Lond. (Zool.), vol. xv., 1880, pp. 212-214. 
