30 



PALEONTOLOGY 



dern seas. The Crinoidea differ from the other echinoderms 

 in having the generative organs combined with the arms, and 

 opening into special orifices near their base. Nearly all 1 la- 



Fig. 6. 

 Crinoidea ; Blastoidea ; Cystoidea. 



i. Sphaeronitcs aurantium, Wahl. ; L. Silurian, Sweden. 



2. Pseudocrinus bifasciatus, Pearce ; U. Silurian, Dudley. 



3. Pentremites florealis, Say ; Carboniferous, Ohio. 



4. Crotalocrinus rugosus, Mill. ; U. Silurian, Dudley. 



5. Poteriocrinus (joint of column) ; Carboniferous, Yorkshire. 



6. Encrinus entrocha ; L. Muschelkalk, Germany. 



7. Apiocrinus Parkinsoni, Mill. ; Bradford Clay. 



8. Pentacrinus basaltiformis, Mill. ; Lias, Lyme. 



9. Marsupites ornatus, Mill. ; Chalk, Sussex. 



genera, except Comatula and Marsupites (fig. G, 9), appear to 

 have been attached either by the expanded base of the column, 

 as in Apiocrinus, or by jointed processes, as in Bourgwticriwus. 

 In many instances the lower part of the column throws out 

 innumerable root-like side-arms, which strengthen and support 

 it. The column is comparatively short in Apiocrirms Parhin- 

 soni, and extremely elongated in PentacHnus Humeri. It is 

 round in nearly all the pala?oz<>ic Crinoids ', and when five- 

 sided, the articular surfaces of the joints arc simply radiated, 

 as in the rest. These joints are perforated in the centre, and 



