PALEOPXEUSTES AXD LEKOPXEUSTES. 183 



270, the labium is quite broad. In P. crvdaiu^, the third plate occapk* 

 nearly its whole flank. Fig. 269, while in P. htfOnx, Figs. 266, 270, in which 

 it is shorter and more arched, the sides of the labium are flanked by the 

 first, second, and third ambulacral plates which are quite small. In Phris- 

 socystis the labium is deeply indent^ by the first plate, Fig. 271. In 

 Argopatagus, Fig. 272, it resembles somewhat that of Phrissocystis, aud is 



Fl«. a<K Fk;. 308. Pig. 27a 



IXSOPXErSTBS lX>5«il5PDrr5. PAUX«PyEr«TK5 CBIPTATTB. Paleop. htstmx. 



flanked for nearly its whole length by the first and second plates. In 

 Genioopatagus, Fig. 273, the labium is mure like that of the Urechinidae. 



In Lmopmntatei Mwrayi^ the labium is small, followed by a long narrow 

 angle plate, while in the West Indian linopneustes the labium is not thus 

 subdivided (PL 92). Lmopmatdes exeaUrieus de Meijere^ has the elongate 

 narrow labium characterbtic of the West Indian Linopmauia lomgufimMZ 

 (PI. 92, figs, i, •?). 



TTie sternum of Pksiazamis hirsvius of M. de Meijere * with its short labium 

 is Tery similar to that of Paleopmemst^ cristatun (PI. 95). Plesiozonus differs 







Pi« 27L P*o. 272. Fl«. 27S. 



pHKUteocTt^ns accxjlata. AMBorxTxcr^ TrrKXTK GExiooPATAcri' AmarnL 



from Linopneustes and Paleopiieastes by ic^ small ambulacral plates alternat- 

 ing near the extremity of the petals with the larger plates. The labium of 

 PtOeopmemsies gpedoAdU and of P.frogiik. as figured by M. de Meijere,* recalls 

 more the labium of Linopneust^ than of Paleopneustes. 



At the ambitus of linopneustes ^Pls. 92; 93; 94. fig. 71. as in Phrisso- 

 cystis (Pis. 88, figai /, 2 ; 90. figs. 1, J), there are a number of very narrow 



•*" KrhmnMm. Ft XXT. figs. 2, 7. ' kL PL XXII. fig. 441 



- SR<c<m ^ ir-*«««g.i«> PL XXTI, fig. 4M. « Id. PL XXL figs. 422, 437. 



