THE ECHINODRMATA 257 



cystids showing this structure form an order Rhom- 

 bifera. 



In specimens much better preserved than usual small 



M 



ABr 



AA 



FIG. 73. CYSTOIDEA. 



a, Dendrocystis scotica Bather, Ordovician, Girvan. ( X |.) Details of plates 

 omitted from brachiole. (After Bather.) b, Lepadocrinus quadri- 

 fasciatus (Pearce), Silurian (Wenlock Limestone). Slightly enlarged ; 

 details of plates on arms omitted. (After Forbes.) c, Glyptosphcera 

 leuchtmbergi Volborth, Ordovician, Pulkowa (Russia). ( X . ) Mouth 

 in centre, with five radiating grooves, irregularly branched, each 

 branch ending in articulation of a brachiole (represented by black 

 spots : where plate-sutures are shown, each of these is seen to be in the 

 centre of a plate). Anus below, black (plates of pyramid missing). 

 Thecal plates only shown around anus. (After Jaekel.) A, Ana) 

 pyramid; A A, anti-anal process; ABr, anti-brachial process; Br., 

 brachiole; M, mouth ; P.R., pectinirhomb. 



arms have been found arising from the mouth, composed 

 of grooved brachial and smaller ambulacral plates. 



17 



