71 
form cirri composed of 18—30 segments, of which the distal are 
little, if any, shorter than the proximal and not compressed later¬ 
ally, and by the long arms composed of long segments, the other, 
comprising A. petasus (Duben & Kor.), bifida (Pennant), moroc- 
cana A. H. Clark, dfibeni Bolsche and Hnpferi Hartlaub, being 
characterized by the short cirri, with generally only 10—15 seg¬ 
ments, of which the distal are laterally compressed and, in lateral 
view, broader and shorter than the proximal, and by the short and 
comparatively stout arms, composed of short segments. 
A considerable part of the material of Crinoids possessed by 
the Copenhagen Museum being at the present time in the hånds 
of A. H. Clark in Washington, I have no opportunity of examin- 
ing all the species mentioned above, but must in the main confine 
myself to a comparative study of the species bifida , mediterranea 
and petasus. 
In case A. petasus should rightly be referred to another genus 
than those species which differ from it in their embryological devel- 
opment ( A . adriatica, mediterranea and bifida — and also A. mo- 
roccana , judging from a statement in a letter from A. H. Clark 
that this is the species studied by Perrier) one should expect to find 
it differing from the other species, at least, in some marked external 
features that could justify a generic distinction. However I fail to 
find any such special feature. It would really seem more natural 
to distinguish as separate genera or subgenera the two groups 
established by Clark 1 ) than to make A. petasus a separate genus, 
distinet from another genus comprising mediterranea and bifida 
and the other species named. A. petasus decidedly agrees with the 
bifida-g roup in the important charracters of the cirri and arms. 
On the other hånd it differs quite markedly from bifida in the 
character of its oral pinnules, these being mueh more thorny in the 
latter. But to ascribe so great importance to this single feature as to 
l ) The character mentioned by Clark as distinguishing the two groups 
that in the mediterranea -group the distal segments of the cirri are not 
compressed laterally, which they are in the bifida -group does not seem 
to me to hold good; they are or (at least) may be just as mueh com¬ 
pressed in mediterranea also. On the other hånd I would add another 
conspicuous difference between the two groups, namely that in the me- 
diterranea -group the first genital pinnule is the fourth, while in the 
other group (at least in the species I have examined) it is the third. 
