VIL. Cyathoerinus. 219 
TIT Br from 3 to 7. The lower numbers are more usual, 
aud the higher numbers, when they occur, are in the branches 
on the inner side of the dichotom; thus, the left posterior 
arm of E 1450 (Pl. XIII. fig. 2) has II] Br, counting from 
left to right, —3.4..6.4%*. eee too, the second ossicle 
is “Hennes higher than She, first 
IV Br from ah to 9. In this case the lower numbers are in 
the branches on the outside of the arm, the higher numbers 
on the inside of the dichotoms, and the middle numbers on 
the inside of the arm. ‘This arrangement will be better 
understood from an actual example: in 57362 B. M. the quarti- 
brachs run thus, from left to right—4.8..9.7-6.6..7.95. 
VeBr from 3 to 11. Generally speaking these tenes 
follow the same sort of arrangement as in previous series, but 
the higher numbers are often finials, especially in rather 
young specimens. ‘Thus in an arm of 57480 B. M. (Pl. XIII. 
tig. 1), starting from the middle or inner side of the arm and 
passing towards the outer side on the right, the numbers run 
as follows, f being placed against the filese. 9..8f.6f 
Og eof 8. 
VI Br from 2 to 14. Many of these are generally finials, 
and in young specimens even the lower numbers are finials. 
Otherwise the arrangement is much as in the quintibrachs 
VII Br are only found in well-grown specimens. The 
numbers observed are 3 and 4. They are always finials ; but 
it is of course conceivable that the arms might branch yet 
once more in an exceptionally well-favoured individual. lif; 
however, finials appear in any one series, it seems to be the 
rule that all of the ensuing series shall be finials; that is to 
say, in no single arm does one branch ever get more than one 
series ahead of the other. 
The above numbers do not take account of 206 Holcroft, 
in which the series are rather longer, 17 being seen in one 
internode. 
Anal structures —The measurements of anal w in K 1450 
are as follows:—Height 45 millim.; width below, 38 
millim. ; width above, 4°75 millim.; that is te say its width 
is about 3 that of the ‘adjacent radials (Pl. XIII. fig. 2). It 
supports a large proximal median plate and a smaller plate 
on either side (rt and ft). The latter plates rest partly on the 
adjacent radials. 
The Ventral Sac is about half the length of the arms or 
* In this and in the ensuing examples the peculiar spacing of the 
numbers is an attempt to represent the bilateral symmetry of the arm: 
the two branches of each dichotom are separated ‘by only a single full- 
stop. 
