H. L. Hawkins — Morphology of Echinoidea. 445 



Periproct.— Ovoid or elliptical, comparable with the peristome in 

 area. Supra-marginal, or on a posterior surface, in Fyrina, marginal 

 in Conulus, infra-marginal in Echinonens. (In young forms of Conulus 

 it may be as high as, or higher than, in adult Pyrina.) 



PYRINA 

 DE.SMOUUNSI 



Analysis of interambulacral tuberculation in Pyrina and Conulus. 



Apical system.— Squarish in outline, built normally of four genitals 

 (the madreporic one being the largest) and five oculars, of which the 

 three anterior plates are minute, while the two posterior ones are 



