ECHINODERMATA. 145 



Pentacrinus MILLER. 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 briar eus MILLER, pp. 56 58, Tab. i. u. Guv. R. 

 Ani. ed. illustr., Zooph. PI. 7, fig. 1, from the Lias-schist. 



The living species of this genus, Pentacrinus Caput Medusae, 

 is found in the Caribbean Sea, and was first described by GUETTAED 

 Mem. de TA cad. Roy. des Sc. 1755 (Paris, 1761) pp. 224, &c. PL 8 10 j 

 another, more mutilated specimen, found on the coast of Barbadoes, 

 was described by ELLIS in 1761, Phil. Transact, vol. 52, p. 357, PI. xm. 

 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. MUELLER ( Ueber den Bau 

 des Pentacrinus Caput Medusae, 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 pinnulce 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 Crino'ids. 

 a) Tesselate. 



Marsupites MANTELL. Marsupiocrinites BLATNV. Calyx of 

 parts calcareous pentagonal striated ; arms ? 



Sp. Marsup. ornatus MILL. Crinoid p. 134, with figure, BKONN, 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. 



6) Articulate. 



Comatula LAM. (Alecto LEACH, MUELL. Cirri dorsal articu- 

 late, around a pentagonal disc. Eadials mostly without basals 



name of Encrinites Sckottheimii of which H. V. MEYER has formed a new genus, 

 Chelocrinus. See the paper of the latter ; Isocrinus und Chelocrinus, Zwei nette Typen 

 u. s. iv., Museum ScnJcenbergian., n. p. 249. 



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