Terms in Crinoid Morphology. 59 
free from the radials upward. Let us now consider it with 
reference to pinnulate arms. 
First in cases where these are free. Strictly speaking the 
first ossicle that bears a pinnule is homologous with the prim- 
axil, and the next one bearing a pinnule with the secundaxil. 
But however philosophical this may be, it is clear that, after 
all, practical people do need some name that shall include all 
the pinnuliferous ossicles of any one series or order. In 
supplying this want we may adopt one of two courses. Hither 
we may retain the present system with its illogical names, or 
we may evolve a new system that shall answer the require- 
ments of a morphological terminology as laid down on 
p- 55. There can be little doubt that the former course will 
recommend itself to those who have to deal only with recent 
Crinoids, the vast majority of which belong to the genera — 
Antedon and Actinometra (Comaster), for the species of which 
poe formule have been constructed by F. J. Bell * and 
. H. Carpenterft. When, however, we consider fossil | 
pinnulate genera, especially in the Camerata, the second 
course would appear to be accompanied by fewer difficulties. 
For descriptive purposes, then, I would propose a termin- 
ology congruous with the Miillerian term “ distichals.” The 
objections to this that were stated above do not apply in the 
case of pinnulate genera, for in them the branching is almost 
always quite regular and does not take place so many times : 
except in formule, it would rarely be necessary to speak of 
any brachials higher than the octastichals. As a rule the 
monostichals correspond to the primibrachs, and there is no 
reason why the latter term should not be employed. In 
Metacrinus and Calamocrinus, however, pinnules are borne by 
the brachials of the first order. In that case the two terms 
do not apply to the same things, and the word “ monostichals” 
must be adopted. 
In cases where some of the proximal series of brachials 
enter into the dorsal cup, these may be called by Wachsmuth 
and Springer’s term “ Fixed brachials ” or “ brachialia fixa;” 
while those outside the limits of the cup will be “ Free 
brachials ” or ‘‘ brachialia libera.” In formule and symbols 
it would have been natural to have expressed the difference 
between the two by enclosing the fixed brachials in brackets. 
Brackets, however, have already been employed by Bell and 
Carpenter, with far less obvious significance, to denote uncer- 
* “An attempt to apply a method of Formulation to the species of 
the Comatulid &c.,’ Proc. Zool. Soc. Lond. 1882, pp. 530-536, 
+ ‘Challenger’ Zoology, vol. xxvi. part Ix., Report on the Comatule, 
pp. 43 et sgq., 1888. 
