156 



EC HINODERMATA PELM ATOZOA 



SUH- KINGDOM III 



Ci/athoa-iiws, Miller, emend. AY. and Sp. (Figs. 259, 260). Dorsal cup 

 cup-shaped, bilaterally symmetrical. IB five, equal. B large ; the posterior 

 one truncated for the support of an anal plate. R five, all simple ; their upper 



faces provided with a facet occupying less 

 than the full width of the plates. Ventral 

 sac rarely extending to more than one-half 

 the height of the arms. The number of 

 costals extremely variable among the rays. 

 Arms rather delicate, composed of elon- 

 gate cylindrical joints, and giving off" numer- 

 ous branches, most of which divide again. 

 Column round. Ordovician to Sub-Car- 

 boniferous ; Europe and North America. 



Lecythocrinus, 

 Miiller, emend. 

 Zittel (Figs. 

 225, 261). 1 

 Like the preced- 

 ing, except that 

 the infrabasals 

 are very small, 

 and entirely 

 concealed by 

 the column. 

 Ventral sac in 

 the form of a 

 long tube, and 

 e composed of 

 numerous, very 

 regularly ar- 

 ranged hexa- 

 :onal plates, 

 o 1 u m n o b- 

 tusely quad- 

 rangular, com- 

 posed of long 

 peripheral canals. 



FIG. 258. 



Homocrinits curtus, Miill. sp. 

 Devonian ; Schonecken, Eifel. 

 , Calyx from the anal side, showing 

 ventral sac and one arm (right and 

 left sides reversed) ; b, Stem ; 

 of stem-joint (after Schultze). 



FIG. 200. 



a, Cyathocrinus longimanus, Aug. Silurian ; 

 Gottland. Crown of the natural size (after 

 Angrlin); b, C. ramosus, Ang. Portion of an 

 arin viewed from the side ; c, Ventral aspect of 

 same (enlarged) ; d, C. mulvaceus, Hall. Sub- 

 Carboniferous ; Burlington, Iowa. Tegnien 

 perfectly preserved ; e, The same after removal 

 of the covering pieces and orals (after Meek and 

 Worthen). 



FIG. 259. 



ntft. Diagram of dorsal 

 cup (after Bather). 



joints, and perforated by a large central and four 

 Devonian ; Eifel. 



Gissocrimis, Ang. (Fig. 262). IB three to five. B five; the posterior one 

 truncated, and supporting an anal plate. Radial facets elliptical in contour. 

 Ambulacra roofed over by alternately arranged covering pieces. Ventral 

 sac long, always laterally folded. Madreporite well defined. Arms long, 

 regularly bifurcating. Silurian ; Gottland and England. Devonian ; Eifel. 



Arachnocrinus, M. and W. Calyx very small, resembling Cyathocrinus in 

 the arrangement of its plates, but forming a bulbous protuberance from which 

 the robust arms stretch out horizontally. Silurian and Devonian ; Europe and 

 North America. 



1 [The type-specimen upon which this genus was founded (L. Eifelianus, Miill.) was regarded 

 by Schultze as an abnormal variety of Ta.rocnnus, and the specific name was changed by him to 

 T. briareus. But Taxocrinus has no such ventral tube, nor has it peripheral canals. In the latter 

 respect Lecytkocrinus differs also from Gissocrinns, with which it otherwise has close affinities.] 



J 



