ECHINODERMATA. 143 



genus Isis, confounding the fossil Encrinus and the Pentacrinus 

 caput Medusae of the existing creation under the name of Isis 

 Asteria. This singular union of an Echinoderm with a genus of 

 Polyps had doubtless an influence upon the later arrangement of 

 LAMARCK, who placed Encrinus (see above, p. 80) amongst the sea- 

 feathers. SCHWEIGGEB, and CUVIER restored it to the proper place, 

 already assigned to it in the middle of the previous century by 

 GUETTARD, who first described Pentacrinus caput Medusce. This 

 whole family belongs rather to the former period of the history of 

 our globe, than to the present. The species now living in our seas 

 are almost all non-pediculate, whilst geological investigation has made 

 us acquainted with numerous forms of pediculate sea-lilies. What is 

 now a youthful mutable form of life was then the prevalent and 

 permanent. The same thing may be observed in other classes also 

 with respect to the fossil representatives of genera that are living 

 at the present time. 



The chief work on this family is : 



J. S. MILLER, Natural History of the Crino'idea, Bristol, 1821, 4to.' 



A. Cr ino'ids affixed, 

 a) Sessile. 



Holopus D'ORBIGNY. Calyx affixed, hollow, undivided, with 

 scattered tubercles. Four calcareous pentagonal parts at the upper 

 margin of the calyx, sustaining four pairs of articulate and pinnate 

 arms. 



Sp. Holopus Rangii, D'ORBIGNY, GUERIN Magasin de Zool. 1837, Cl. x. PI. 3; 

 from the Caribbean Sea at Martinique. Both in the want of a stem and 

 the number of the arms this genus differs from the other Crino'ids. 



b) Pediculata. An articulate column sustaining the calyx. 

 * Tesselata. Calyx non-articulate, 

 a) Rays or arms none. 



Genera : Sphceronites HisiNGER, Pentatrematites SAY (Pentremites 

 GOLDF.), Echinosphcerites WAHL., Hemicosmites GRAY, Sycocystites 

 v. BUCK. 



Fossil genera from the Transition- and Mountain-limestone. Comp. BRONN, 

 Lethcea geognostica 1835, Tab. IV. fig. i, &c. According to the opinion of 

 some these were pediculate Echini. 



j3) With rays. 



1 See also W. BUCKLAND, Geology and Mineralogy, London, 1835, pp. 416 442. 



