MORPHOLOGICAL PART. 69 
Miiller’s interpretation of these plates was somewhat modified by 
Schultze,* who assumed that the arms begin invariably with the first well- 
defined articular facet. He held that in Actinocrinus and Rhodvcrinus, which 
have no articulation above the (first) radials, the arms commence above the 
first axillary; but that in Crinoids in which the rays are free above the first 
plate, the arms begin with the second plate of the ray. 
Zittel,t who accepted Schultze’s views and applied them to the later 
Crinoids, describes Hncrinus, Pentacrinus, and Millericrinus with one radial 
followed by two brachials; Apioerinus, however, with three radials. He evi- 
dently supposed that in the latter the first articulation occurred on the axil- 
lary, which is not the case, as shown by Carpenter, $ who found in several 
species of that genus at the upper face of the (first) radial a transverse ridge 
with muscular fosse above it. A similar structure, he believes, exists in all 
Apiocrinide, perhaps with the exception of Guettardicrinus, which, according 
to de Loriol,§ has no articular facets on either of the three “ radials,” nor 
even on the distal faces of the axillary, so that it cannot be determined in 
this genus what plate of the ray bears the first facet. This shows that 
Schultze’s rule does not readily apply in this group. Still more serious diffi- 
culties arise among the Palxocrinoidea. In most of the Camerata, all plates 
of the calyx up to the top of the distichals, and often much higher, are 
closely and immovably united, and the lowest articulation or mobility occurs 
at the base of the arms. 
Applying Schultze’s definition to the Camerata, it is quite evident that all 
the plates of the dorsal cup ina radial direction had to be called radials, 
and not merely those up to the first axillary. This we did in our earlier 
writings; and instead of making the lower facet the division between 
radials and brachials, we took the calyx for the boundary line, and referred 
to the radials all plates of the rays which take part in the calyx, and to 
the brachials the plates of the free arms. We thus recognized among the 
Camerata an indefinite number of radials, while their number was reduced 
in the Inadunata to a single ring of plates, a course which was afterwards 
adopted by S. A. Miller, S. H. Williams, and Prof. Worthen, against Hall, 
Meek, and others, who included in this group the first order of brachials. 
The Ichthyocrinidz, in which the lower branches of the rays take part 
* “ Monographie der Hchinodermen des Eifler Kalkes,” 1866, Wien, pp. 5 und 9. 
+ Handbuch der Paleontologie, Vol. I., p. 339. 
{ Ann. and Mag. Nat. Hist., Ser. 6, Vol. VI., p. 12. 
§ “ Paléontologie Frangaise,Jurassique,” Tome XL., Pt. I., p. 215. 
