MORPHOLOGICAL PART. 69 



Mliller'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 Adinocrimis and RhodocriniiSyVi\nQh. 

 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 Encrinus, Peiitacrinus^ and Millericrimis with one radial 

 followed by two brachials ; Apiocrimis, 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 fossae above it. A similar structure, he believes, exists in all 

 Apiocrinidae, 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 Palseocrinoidea. 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 in a 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 Ichthyocrinidae, in which the lower branches of the rays take part 



* " Monographie der Echinodermen des Eifler Kalkes," 1866, Wien, pp. 5 und 9. 



f Handbuch der Palaeontologie, Yol. I., p. 339. 



% Aim. and Mag. Nat. Hist., Ser. 6, Yol. YI., p. 12. 



§ " Paleontologie Eranpaise^Jurassique," Tome XL, Pt. I., p. 215. 



