REPORT ON THE CRINOIDEA. 125 
the basals and enter two adjacent radials (Pl. XXIV. figs. 7--9; Pl. LVIII. figs. 2, 3, ar) 
There are thus two apertures on the upper surface of each basal, and two on the under 
surface of each radial (Pl. XII. figs. 11, 14, 22, 25; Pl. XVIII. figs. 5, 7; Pl. XX. figs. 2, 
3, 6,9; Pl. XXI. figs. 6a, 60, 6c, 7a, 7b; Pl. XXX. fig. 5,7, 8; Pl. L. fig. 5). As the 
two cords which enter each radial converge towards its distal surface, each of them is 
joined laterally by a commissure to its fellow in the next radial which springs from the 
same primary trunk as itself. These lateral branches form the interradial, and by far the 
larger portions of a circular commissure which unites the five pairs of cords within the 
radials (PI. XXIV. fig. 9,c.co; Pl. LXII.); while the two converging cords within the 
substance of each radial are also united by a very short intraradial commissure (Pl. XXIV. 
fig. 9, 2.co). 
This circular commissure occupies a canal which traverses the radials from side to 
side, lying in the Comatulz very close to their distal face, but more centrally in the 
Pentacrinidee. Its openings on the lateral faces of the radials are shown in Pl. XII. 
figs. 11, 22; Pl. XX. fig. 6; Pl. XX. figs. 6a, 6b, 6c; Pl. XXX. figs. 5, 8. 
The two secondary cords within the basals and the proximal parts of the radials of 
Pentacrinus are more widely separated than the corresponding structures in the Comatulee 
(Pl. XXIV. figs. 7,9; Pl. LVIII. figs. 1, 2—ar), so that the intraradial commissure is 
better defined (Pl. XXIV. fig. 9, 7.co). Beyond the circular commissure the two axial 
cords of each ray lie very close together, though still distinct, just as in the Comatule. 
Each of them forks in the axillary, and there is the same horizontal commissure as was 
deseribed by Ludwig in Antedon rosacea. 
So far as the fossil Neocrinoids are concerned, Hnerinus and Apiocrinus seem to have 
had an arrangement of the axial cords essentially similar to that prevailing in the 
Pentacrinidee and Comatule. In the former genus, as already pointed out by Ludwig, 
no canals have been described either for the intraradial commissure or for the horizontal 
commissure in the axillary; while the secondary radial cords remain distinct as far as 
the axillaries, even to the extent of being lodged within separate canals in the second as 
well as in the first radials. The double eanals are continued through the whole length 
of the arms; and in some species these consist, after the base, of a double row of joints, 
each of which is pierced at its inner end by the two canals. The absence of any canals 
which could lodge an intraradial commissure is very singular; and it is also remarkable 
that the interradial portions of the circular canal should lie so completely in the distal 
parts of the radials. They only join the axial canals where these open on the distal 
faces of the radials; so that if an intraradial commissure were present at all, it must have 
lain just at the edge of the first radials, almost among the ligamentous bundles uniting 
them to the following joints. 
The axial cords of Enerinus were lodged in canals throughout their whole length, 
those within the basals occupying grooves within the substance of the plates which were 
