OUDHK V 



CRINOIDEA ARTICULATA 



173 



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Family 8. Pentacrinidae. d'Orbigny. 



( 'l>ix small, bowl-shaped, ami with dicydic base ; but the infrabasals are either 

 ni'liniiiifiini, <>f 'o,//,///, /,-/// ft-sin'lif.d in tlie adult state. The top stem-joint always the 

 youngest joint of the column. Basals five, radials five, costals one to two. Tegmen 

 flexible, studded with small, irregular, calcareous particles or delicate plates. Arms 



niiuu rinidii lfnn<-hin'j, 

 pinnulate. Column long, 

 r or sub-pentagonal ; 

 angles interrudiatty 

 tJie cirri given off 

 radially. Upper and lower 

 faces of the stem -joints orna- 

 '! with a quinquelobate 

 figwrt. Trias to Recent. 



Pentacrinus, Miller (Iso- 

 crinns, v. Meyer; Cladocrinus, 

 Ag. ; Cainocrinus, Forbes), 

 (Fig. 290). IB obsolete; 

 costals rarely more than two, 

 none of them pinnulate. 

 Arms very!! numerously 

 divided. Column more or 

 less pentangular ; the angles 

 of the axial canal, contrary 

 to the general rule in dicyclic 

 forms, are radially directed, 

 so as to correspond with the 

 outer angles of the stem. 

 Cirri very numerous ; stem 

 not thickened at its distal 

 end. Trias to Recent ; maxi- 

 mum in Lias. 



Exquisitely preserved 

 specimens are found in the 

 Lower Lias of England, and 

 the Upper Lias in the vicinity 

 of Boll and Metzingen, 

 Wiirtemberg. A slab con- 

 taining no less than twenty- 

 four perfect crowns of P. 

 subangularis, Miller, with 

 long intertwining stems, is 

 preserved in the Tubingen Museum. There also may be seen a column 

 which Quenstedt traced for over 70 feet, without reaching either end. 



M"facrinus, Carp. Differs from Pentacrinus in that the Pi are succeeded 

 by four to seven costals, of which the first and second form a syzygy. Where 

 seven costals are present, the fourth and fifth are also united by syzygy. 

 Angles of axial canal interradially disposed, so as to alternate with the outer 



Pentacrinus (Extracrinus) briareus, Mill. Lower Lias ; Lyme 

 Regis, England (after Goldfuss). a, Stem-joints of P. subangutarit, 

 Mill. Upper Lias ; b, Column of /'. basaltiformis, Mill. Middle Lias. 



