274 PROCEEDINGS OF THE NATIONAL MUSEUM. VOL: XXXIV. 
ular and muscular fossx are similarly, to a greater or less extent, 
misplaced. The remaining brachial articulations are all of this type, 
except, of course, in the case of syzygia. This offers another means 
of arriving at the homologies of the joints; granting that the articula- 
tion between the fourth and fifth joints corresponds to 
that always found (in a ten-armed type) between the 
second and third free brachials, and counting backward, 
we find that the preceding joint is the equivalent of the 
first free brachial, the one before that of the costal 
Fi¢.1—Cenrro- aXillary, which in this case is united to the first costal 
hapiat racuy DY Syzygy, therefore reaching exactly the same result as 
or Pentame- we did through a consideration of the pinnule arrange- 
roxrcrs, -s Ment, and the arrangement of the first two syzygia. 
The HLudiocrinus japonicus group, however, differs 
from the /. éndivisus group in the enormous disk, which is black, 
and extends far up on the arms, and in the great amount of separa- 
tion of adjacent radial facets (figs. 1, 2) from all other 
comatulids, except Decametrocrinus. The long, brittle, 
and slender, much compressed cirri, with a long, nearly 
straight, terminal claw, are very characteristic, though 
an approach to these conditions is found in Thysanometra. y44 5 vpy- 
Judging from the character of the radial facets and the  rran view 
extensive centrall cavity, ol | them centno-dorsall, mau hen ym) see 
japonicus group and Decametrocrinus come nearest to PeNnrame- 
certain genera of the Antedonide, such as Thawmato- (i . 
metra, Psathyrometra (fig. 3), etc., and it is found that 
the general character of the pinnules, arms, and cirri also suggest 
the same relationship. 
The proximal arm structure of the Ludiocrinus japonicus group 
and of Decametrocrinus is, however, radically different 
from that of all other comatulds, except Thaumatocrinus, 
ASeche §with which genus it agrees. 
7 In the ordinary. type of comatulid with ten arms 
(fig. 4) there are two costals, united by synarthrial artic- 
ulation, the median ridge on the joint faces appearing 
entra eo externally in the middle of the line of articulation, its — 
rro-porsat position being. usually marked by more or less of a 
AND RADIAL “(lorsal tubercle. On each of the distal” faces of the 
FACES OF PSA- 5 , 5 : . 
ruyrome- aXillary (second) costal is a first brachial, the articula- 
TRA FRAG- tion between the two being the same as that between the 
ie radial and first costal; this jomt never bears a pinnule; 
articulating with the first brachial on its distal face is the second 
brachial, the articulation between the two being synarthrial, as 
between the two costals; but the articulation between the second 
and third (and all succeeding brachials, except syzygial pairs) 
is of the same type as that between the radials and first costals 
