REPORT ON THE CRINOIDEA. 3 
plates which make up each of these rings (PI. XII. figs. 1, 2, 11-16, 22-25; Pl. XVIII. 
figs. 4-7 ; Pl. XX. figs. 1-3, 6-9; Pl. XXI. figs. 6,7; Pl. XXIV. fig. 6, Jb; fig. 7,1, 1b, L; 
Pl. LVIII. fig. 1, 7, 1b; fig. 2, Z). The radials of Bathycrinus are likewise united in this 
way (Pl. VIIb. fig. 4,2); but the sutures between the basals seem to be of a still closer 
nature. They are visible externally in young individuals but disappear in the adult, so 
that the “base” seems externally to consist of but one single piece! (Pl. VIIa. figs. 12-14). 
Sections through a decalcified specimen show, however, that it is really composed of five 
parts like the base of Pentacrinus (Pl. VIIb. fig. 2, B). These five parts are, nevertheless, 
very closely anchylosed. No parallel fibres of connective tissue pass between them, such 
as unite the five first radials together (Pl. VIIb. fig. 4,7). But the organic basis of the 
skeleton is much less close, if not absent altogether, along five lines which radiate out- 
wards from the chambered organ and indicate the position of the sutures. They stain 
less deeply with hematoxylin than the surrounding tissue, but do not reach the exterior 
of the section (Pl. VITb. fig. 2). Neither are they visible in sections through the top 
and bottom of the basal piece; and but for the knowledge obtained in this way, the 
basal piece would probably have been described as an uppermost stem-joint, as has 
actually happened in the case of Rhizocrinus. 
In some individuals of Lhizocrinus lofotensis (Pl. IX. figs. 1, 2) there are no 
indications of suture, even in the adult; though in others the sutures are visible 
externally (Pl. X. fig. 2). In the former case the nuclear connective tissue network is 
continuous through the whole section, which exhibits no unstained radiating lines, as do 
similar sections of Bathycrinus. There is a marked difference between the two genera, 
however, as regards the lateral union of the radials. Those of Bathycrinus are united by 
synosteal fibres (Pl. VIIb. fig. 4, 2), just as in Pentacrinus (Pl. XXIV. figs. 7-9 ; 
Pl. LVI fig. 2, Z) and Comatula. But those of Rhizocrinus are much more closely 
connected, just in fact in the same way as the basals of Bathycrinus are. No ligamentous 
fibres are visible in horizontal section, but only five (or six) radiating lines where the 
nuclear network is incomplete (Pl. VIIa. fig. 6). The radials in this type, and the 
basals in Bathyerinus, seem to be united by a limestone deposit which has different 
characters from that usually found in Echinoderms ; and I think it will be advantageous 
to denote this by the term “anchylosis,” reserving “synostosis” for cases in which 
ligamentous fibres are concerned in the union of the joints; though both of them, like 
the “syzygy,” would be considered as sutures. 
Smooth sutural unions like those between the basals and radials, though somewhat 
less close in their character, occur at intervals in the stem of the Pentacrinide, every 
nodal or cirrus-bearing joint being united in this way to the joint below it (Pl. XIX. 
figs. 3, 4; PL. “XX1E figs. 16, 20, 21; Pl. XXVI. figs. 12-16; PL XXXI. fig. 3; 
1 This must be carefully distinguished from the “article basal” of the Apiocrinide, which is the uppermost 
stem-joint that supports the basals. 
