CLA.SS III 



CRINOIDEA 



233 



of the axial canal, contrary to the general rule in dicyclic forms, directed 

 radially, corresponding with the outer angles of the stem. Stern of great 

 but unknown maximum length, having been traced for twenty feet without 

 reaching the end ; cirri very numerous, compressed or elliptical in section. 

 Lias and later Jura ; Europe. 



The Crinoids of this geiius were 

 very gregarious, and flourished in 

 immense colonies. Exquisitely i)re- 

 served specimens are found in the 

 Lower Lias of Lyme Regis, Eng- 

 land, and in the vicinity of ßoll 

 and Metzingen, Würtemberg, which 

 have served as types of illustra- 

 tions in numerous works on Paleon- 

 tology. A slab containing no less 

 than twenty-seven perfect crowns 

 intertvvined with stems and cirri, 

 raay be seen in the U.S. National 

 Museum at Washington. 



Isocrinus Meyer {Isis Linn. 

 pars; Encrinus hsunsirck pars ; 

 Cainocrinus Forbes ; Ficteto- 

 crinus de Loriol ; Neocrinus 

 Wy V. Thomson ; Pentacrinus 

 sensu P. H. Carpenter). IBB 

 so far as known, present in 

 the adult, but visible only 

 when stem is removed. BB 

 forming a complete circlet, 

 or minute and separated by 

 lower angles of BE. Eadials 

 notprojecting down ward over 

 proximal columnals. Arms 

 about regularly dichotomous. 

 Columnals of circular, penta- 

 gonal or stellate section ; 

 sectors of joint-face distinctly 

 petaloid, with coarsely crenu- 

 late edges. Trias and Juras- 

 sic; Europe and North 

 America. Eecent ; "West 

 Indies (5-531 fathoms). 



Balanocrinus Agassiz in 

 Desor. Columnals of circular 

 or hexagonal section, with crenellae around the edge only, not along the 

 sides of the sector. Trias to Eocene ; Europe. Known from fragments only. 



Austinocrinus de Loriol. Columnals have a Joint surface as in Isocrinus, 

 but with finer Striae radiating from the petals. Cretaceous ; Europe. 



Cenocrinus Wyv. Thomson. Recent ; West Indies (5-531 fathoms). 



Endoxocrinus A. H. Clark (Diplocrinus Döderlein). Infrabasals resorbed 

 in the adult. Arms heterotomous, in two main rami with branches to the 

 inside of the dichotom ; the divisions are at the outer side of the rays only, 

 and consist each of two joints, united by syzygy. Kecent ; West Indies. 



Fig. 837. 

 Pentacrinus (Extracrinus) fosfdlis Blum. Lower Lias ; Lyme Regis, 

 England (after Goldfuss). a, Stem-joints of P. subangularü Mill. 

 Upper Lias ; b, Column of P. hascUtiformis Mill. Middle Lias. 



