REPORT ON THE CRINOIDEA. 55 
only small ones. The arms, however, reach an enormous development, and Quenstedt 
calculates the total “ Krone” to contain not less than five million pieces.’ 
In the recent Pentacrinidze the arms are generally well developed in proportion to 
the stem. This proportion is of course least in young individuals, as shown in 
Pls. XXXV. and LI., while it is greatest in forms like Pentacrinus miilleri, Pentacrinus 
maclearanus, Pentacrinus wyville-thomsoni, and Pentacrinus alternicirrus (Pls. XIV., 
XVI., XIX., XXV.). These lead a semi-free existence, owing to the fracture of the stem 
at a node, as was probably also the case in Eutracrinus briareus with its large 
“Krone? 
Among the Comatulide the vegetative system is reduced to a minimum, as they have 
no stem in the adult condition. The arms, however, are often very extensively developed, 
far more so than in any recent Pentacrinide. The ultimate arms of a Pentacrinus or 
Metacrinus do not often exceed forty in number; and they rarely consist of more than 
one hundred joints, though twenty or thirty more may intervene between the last 
axillary and the calyx (Pls. XIV., XVI; Pl. XVIII. fig. 1; Pl. XIX. fig. 1; Pl. XXV.; 
PL XMVIUL. figs Us) Pl) XXX. fig.1; Pl. XXXIV. fig. 1; Pls. XXXVML,'XIk, XUIL- 
Bie fee Ele SUING fies? » PL XLV. figs U2 Pls, XVI, KEVIN: PL XLS 
fig. 1; Pl. LIT. fig. 1). On the other hand, although there are quantities of ten-armed 
Comatule, very many species, especially of Actinometra, have from forty to sixty arms; 
some, like Actinometra bennetti, and Actinometra schlegeli, eighty or more; and in a few 
gigantic types like Actinometra nobilis’ there may be over one hundred arms. Further, the 
number of arm-joints is generally from one hundred and twenty to one hundred and fifty, 
apart from the syzygies ; while in a large Antedon eschrichti or Actinometra bennetti and 
in other multiradiate species of the latter genus there may be over two hundred arm-joints. 
Nearly all of them bear pinnules, which are often very long until quite near the arm ends. 
But in Metacrinus and also in Pentacrinus, though to a considerably less extent, the 
development of pinnules stops short some little way from the extremity of the arm ; and its 
outermost segments bear little stumps of two or three joints only, or may even show no 
signs of pinnules at all (Pls. XXV., XXVIII, XXXI., XXXIV., XXXVIIL, XL., XLIL; 
Pl. XLII. fig. 4; Pls. XLIV., XLVI., XLVIIL, XLIX., LL, LIL). 
The same peculiarity is repeated on a smaller scale in the ambulacral plates of the 
pinnules. Those of Comatule (when present) are continued almost to the end of the 
pinnule (Pl. LIV. fig. 6). But in the Pentacrinide the last few pinnule joints, some- 
times even four or six, are totally devoid of any ambulacral plating (Pl. XV. figs. 7-9; 
RES Siete ehh Xl hey 9) PE XLVIL fig, 10; Pl) XLIX: fig. 7; Pl Ep 
fig. 5). The same is the case with the extremities of the arms. In fact, both in the 
persistence of the stalk and of the external basals, and also in the nature of the arms, 
1 Encriniden, p. 292. 
* The specific formula of this type is—a.3. 5 .3.3. ; : 
