650 PEKISCHOECHIN1DAE. 



Desmosticha they form more or Less regular lateral arcs. We have thus a 

 much less marked difference between the two suborders than would appear 

 on first analysis. We know nothing as yet of the mode of formation of the 

 additional rows of plates either in the ambulacra] or interambulacral system; 

 this would throw great light on the homologies of this suborder. 



