CRINOIDEA. 



33 



modern genera. The body of the Crinoid is composed of poly- 

 gonal plates forming a cup, which is covered by a canopy of 

 smaller plates. The month is often proboscidiform ; the anal 

 orifice is near it. The five arms which crown the cup are 

 sometimes nearly simple, but feathered with slender, jointed 

 fingers; in other genera they divide again and again, dichoto-' 

 mously; and in two remarkable Silurian forms, Anthocrinus 



Fig. 6. 

 Crinoidea ; Blastoidea ; Cystoidea. 



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



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



3. Pentremites tiorealis, Say; Carboniferous, Ohio. 



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



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



6. Encrinus entrocha ; L. MuscJielhalk, Germany. 



7. Apiocrinus Parkinsoni, Mill. ; Bradford Clay. 



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



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



and Crotalocrinus (fig. 6, 4), these subdivisions are extremely 

 numerous, and the successive ossicles are articulated to each 

 other laterally, forming web-like expansions, similar in appear- 

 ance to the coral Fenestrella (fig. 3, n). Other remarkable 

 Silurian Crinoids belong to the genera Glyptocrinus Eucalyp- 

 tocrinus, Geocrinus (the "Dudley Encrinite") and Caryocrinas. 

 Several are common to the Silurian and Devonian, as Me- 

 locrinus, Cyathocrinus, and Rhodocrinus; the two last, and 



D 



