ECHINODERMATA. 145 
Pentacrinus Minter. Column not incrassated towards the top, 
pentagonal with joints having a pentapetalous mark. Cirri adher- 
ing to the column in whorls. 
The fossil species of this genus belong to the oolite period, as 
ex. gr. Pentacrinus briareus Mtuurr, pp. 56—58, Tab. 1. 1. Cuv. R. 
Ami. éd. illustr., Zooph. Pl. 7, fig. 1, from the Lias-schist. 
The living species of this genus, Pentacrinus Caput Meduse, 
is found in the Caribbean Sea, and was first described by GuEerrarp 
Mém.de? Acad. Roy. des Se. 1755 (Paris, 1761) pp. 224, &c. Pl. 8—10; 
another, more mutilated specimen, found on the coast of Barbadoes, 
was described by Exits in 1761, Phil. Transact. vol. 52, p. 357, Pl. xu. 
Specimens of this species are rare in Museums, seven only, as far 
as is known, existing in the different Cabinets. The most complete 
description was given not long ago by J. Murtter (Ueber den Bau 
des Pentacrinus Caput Meduse, Berlin, 1843, folio). The stem of 
Pentacrinus has no muscles, but is merely passively motile or flexible 
by means of fibrous bundles and an elastic tissue between the joints. 
The arms and pinnule are moveable by muscles without transverse 
stripes ; these muscles are situated on the side corresponding to the 
mouth, and can only flex the parts: extension, or motion outwards, 
seems to be effected merely by the elasticity of the parts. The 
growth of the joints of the stem occurs in the part at the top 
nearest to the calyx, which corresponds to what is observed in the 
growth of the joints in worms and entozoa. 
B. Free Crinoids. 
a) Tesselate. 
Marsupites MANTELL. Marsupiocrinites Buatny. Calyx of 
parts calcareous pentagonal striated ; arms ? 
Sp. Marsup. ornatus Miu. Crinoid p- 134, with figure, Bronn, Leth. Tab. 
XXIX. f. 13; (Tab. xxxiv. fig. 9, with conjectural restoration of the arms 
after the figure of MANTELL); fossil from the chalk-period. 
b) Articulate. 
Comatula Lam. (Alecto Leacn, Murwu. Cirri dorsal articu- 
late, around a pentagonal disc. Radials mostly without basals 
name of Encrinites Schottheimii of which H. V. Meyer has formed a new genus, 
Chelocrinus. See the paper of the latter ; Isocrinus und Chelocrinus, Zwei neue Typen 
u. s.w., Museum Senkenbergian., 11. p. 249. 
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