OT Fe LOR re eC 
ae a prea ae ee ibe s/n 
234 THE VOYAGE OF H.M.S. CHALLENGER. 
eight pinnules which contain the short fusiform genital glands show this feature most 
distinctly. Somewhat the same character presents itself in the enlarged lower portions 
’ of the long pinnules of Hyocrinus. But in this case the plate-like sides of the pinnule- 
joints diverge considerably, so that the median groove is widened instead of narrowed as 
in Bathycrinus. It is therefore partially roofed in by side plates (Pl. Ve. figs. 9, 10), 
of which there is no trace in Bathycrinus. But the plate-like sides of the joints bound a 
narrow ventral furrow, just as in the arms, and the covering plates rest directly upon 
their edges (Pl. VIL. figs. 7, 8; Pl VIII. figs. 3, 5), as is the case in Rhizocrinus and in 
the outer parts of the pinnules of Hyocrinus (Pl. Ve. fig. 9; Pl. IX. fig. 4; Pl. X. fig. 20). 
They are continued down the sides of the arm-grooves on to the disk, and in Bathycrinus 
aldrichianus, which has no orals, they stand up all round the edge of the peristome, as is 
represented, though badly, in Pl. VII. fig. 3. These covering plates are scarcely so 
substantial as the corresponding plates in Hyocrius, and are also narrower, though nearly 
as long. 
The two lower brachials and part of the third assist im the protection of the visceral 
mass, the upper surface of which is more or less strongly convex (Pl. VIL. fig. 3). There 
is a very large, funnel-shaped peristomial opening, at the bottom of which is the mouth, 
and the anus is on a low papilla in one of the five interradial areas. In Bathycrinus 
carpentert these are supported, according to Danielssen and Koren, by large retiform 
caleareous plates a little sunk in the perisome, which are obviously persistent orals, 
though they seem to be entirely absent in the three other species of the genus. In his 
preliminary description’ of Bathyerinus aldrichianus Sir Wyville Thomson said “ the 
disk is membranous, with scattered calcareous granules. The mouth is subcentral; there 
are no regular oral plates ; but there seems to be a determination of calcareous matter to 
five interradial points round the mouth, where it forms little irregular calcareous bosses.” 
This description was accompanied by a woodcut which was definitely stated to represent 
the Bathycrinus from Station 106 (in Mid-Atlantic), and not one of the numerous 
specimens obtained at Stations 146 and 147 inthe Southern Ocean. The whole set were at 
first regarded by Sir Wyville Thomson as belonging to one and the same species, to which 
he gave the name Bathycrinus aldrichianus ; but he subsequently limited this name to 
the individuals from the Southern Ocean. They are figured on Pl. VII., which was lettered 
and printed off before hisdeath. The disk of one of them isshown on Pl. VU. fig. 3, and 
obviously bears neither scattered calcareous granules nor interradial bosses round 
the mouth. This individual has not come into my hands; but the disk of another which 
I have examined is perfectly naked, except for the covering-plates at the sides of the 
ambulacra, and the peristome is like that shown in fig. 3. The specimen which was 
obtained at Station 106, and had been already figured in the Journal of the Linnean 
Society as Bathycrinus aldrichianus, was drawn by Mr. Black for P]. VIII. ; but on one 
1 Journ. Linn. Soc. Lond. (Zool.), 1876, vol. xiii. pp. 50, 51 ; also in The Atlantic, 1877, vol. ii. pp. 92-95, fig. 23. 
