24 



SVEN LOVEN, ECHINOLOGICA. 



to the next, and so on. For, a.s sooii almost as a projection 

 has attained its full size, it is subjected to the reduction so 

 manifest externally. It is gradually thinned oif by reabsorp- 

 tion, now niore in its iipper part, fiQ- -^^ i^ow more in the 

 lower, fig, 4, and löses its verruca. And while the projection 

 on which the muscle is attached thus gives way, the next 

 plate rises and takes its place, to be backed in its turu by 

 tlie third, and so forth. In this manner the movement goes 

 on that maintains in full strength the supports of the masti- 

 catory muscles. 



Auricle of Cidaris papillata Leske. 1. Adoral side. 2. Aboral side. ." — f). Sections. 



These supports, divergent projections developed from the 

 interradia as successively renewed continuations of their sub- 

 stance, are functionally analogous to the auricles of the Ecto- 

 branchiates, but morphologieally very dilferent. Still it will 

 be convenient to let them bear the name of auricles. 



In the great division of the Ectobranchiates the mode of 

 growth of the corona is essentialty the same as in the Cida- 

 ridse. The new plates are added at the dorsal margin of the 

 last-formed ones, there is an incessant downward movement, 

 and a continual disintegration at the margin of the peristome. 

 Like the Goniocidaris the still astomous Echinid has the pri- 



