. 
REPORT ON THE CRINOIDEA., 253 
externally, and their upper and under faces approach one another rather sharply, owing 
to the convexity of the upper surface of the basals, so that their inner ends are very thin. 
The centre of the funnel which they form is occupied by the compact plug of close cal- 
careous network which was mistaken by Sars for a basal rosette (Pl. VIIIa. fig. 7; Pl. X. 
figs. 1, 4—br). This is attached firmly to the inner ends of the radials, and comes away 
with them. It les on the top of the convex upper surface of the basals, the sloping sides 
of which are divided into fossee for the reception of the radials. Close to the 
inner end of each fossa is an elongated opening; and there is a similar one at the 
centre of the inner end of each radial ; but it is not exposed 
until after the removal of the central plug. Ludwig’s view, 
however, requires that there should be an opening at the inner 
lateral angle of each radial and none in the centre, as is really 
the case. The inference from this fact is that the primary 
interradial cords actually fork in the basals, and that the left 
branch of one fork, and the right branch of the next one pass 
out together through one of the elongated openings on the 
upper surface of the basal ring, which crosses the line of the — Fie, 18—Diagram of the distribution 
interbasal suture. I find this to be actually the case. Rhdzoerinus lofotenss. By Tusa 
R, radials ; 51, first brachials. 
Sections through the uppermost part of the basal ring, above 
the level of the chambered organ, clearly show the forking of the primary cords, 
though no interradial lines of suture are visible at these points, as should be the 
case on Ludwig’s theory of the composition of the calyx. At the same time I can 
readily understand how the use of the section-method alone led him to fall into this 
error. For owing to the convexity of the upper surface of the basals, a horizontal 
section through their central upper part might pass through the lowest and outer edge of 
the radial pentagon, and thus show interradial sutures, although the central portion of 
the section with the forking cords really belonged to the basals. The question is not a 
very important one; and but for my having been able to examine a dissected calyx, the 
exclusive use of the section-method would have led me to follow Ludwig’s description, ex- 
cept in one point. He does not seem to have noticed the presence of the intraradial commis- 
sures first described by himself in Antedon ; for he neither mentions them, nor introduces 
them in his diagram and figures. The special interradial commissures are of course absent, 
being unctionally replaced by the secondary interradial cords; but every two of these which 
converge within the substance of a radial are united by an intraradial commissure, just as 
they are in the Comatulz. This is clearly distinguishable in both the series of horizontal 
sections which I have cut through the calyx of Rhizocrinus lofotensis (Pl. VIIa. fig. 6, 2co). 
The distribution of the axial cords in the calyx of Rhizocrinus is thus somewhat 
different from that described by Ludwig, as will be seen if the accompanying woodcut 
(fig. 18) be compared with fig. 18 on Taf. vi. of his memoir. 
