The CalceocrinidcB. 397 



Anal tube large, heavy, and occupying the centre of the posterior 

 side; column round. 



Consolidated basal piece triangular, with the posterior angle abruptly 

 truncate at the columnar facet, where it is rounded up. It is composed 

 of four plates, the two anterior of which extend to the column by at- 

 tenuated processes; their outer portion occupies the middle of the an- 

 terior base-line, and does not extend to the lateral angles; suture-line 

 between them and the lateral basals sinuous. 



Second ring consisting of six plates; anterior radial high and very 

 narrow, supporting the lower face of the anterior brachial. Lateral 

 radials large, pentagonal, with the lateral angle prolonged to meet the 

 lateral processes of the azygous plate. 



Posterior radials rather large, triangular, and each inclosed between 

 the proximate lateral radial, the basal, and the azygous. 



Azygous plate broadly T-shaped, and consisting of a middle portion 

 or body, an inferior arm which extends between the posterior radials to 

 the arch around the basal plates, and two lateral arms which meet the 

 processes of the lateral radials, inclosing the posterior radials beneath 

 them; their anterior surface supports the large anal plate. These lat- 

 eral arms and central body probably represent the first anal plate, 

 while the inferior process is representative of the azygous plate which 

 has been anchylosed to it. 



Plates of the ventral tube large quadrangular. First anterior brachial 

 broad. Lateral brachials two, the second of which is axillary; beyond 

 this the lateral arms undergo regular bifurcations at every third or 

 fourth joint. No pinnules observed. 



Vault depressed below the margin of, and formed by processes from, 

 the four plates forming the rim of the calyx, i. e., the anterior and 

 lateral radials and the azygous. 



Column of medium size, with joints of the curved end arched from 

 side to side so as to fit the antero-posterior depression of the columnar 

 facet. 



Type of genus, Prodivocrinus radiculus Ringueberg. 



Since the original description of the type was published, a 

 number of other specimens have been found which more clearly 

 elucidate points of structure not shown in the type specimen, or 

 obscured by adherent shale, since removed, in that specimen; 

 so that a partial redescription becomes necessary. 



Prodivocrinus radiculus Ringueberg. 



PI. X., Fig. 6. 



Calceocrinus radiculus Ringueberg. Jour. Cin. Soc. Nat. Hist., Vol. 

 v., p. 120, 1883. 



