PODOCIDARIS. 405 



lation surrounding the primary spines is limited much as in A. Dufresnii, and 

 in spite of the striking differences thus far noticed in these two species, it 

 may be that A. stellata and A. Dufresnii may turn out one species. From in- 

 ability to decide, for want of material, which of these two species of Arbacia 

 Blainville intended to denote by this name of stellata, as it is eminently 

 applicable to both, the young specimens of this species were described by 

 myself, and afterwards by Dr. Liitken, under a new name. . An examination 

 of the originals leaves no doubt as to which cf the two species Blainville 

 intended to apply the name. 



The large, prominent abactinal system, with its pointed genital plates, 

 projects into the bare median interambulacral spaces ; a marked star-shaped 

 pattern is seen from above, owing to the peculiar pattern of coloration of 

 the genital plates of the median sutural interambulacral line. Actinal cuts 

 extremely shallow ; lips of cuts long, but not marked. 



The prominence of the interambulacral sutural lines of 3"oung specimens 

 is quite marked. The genital plates on the edge surrounding the anal system 

 are covered by miliaries, differing in this respect strikingly from all speci- 

 mens of A. Dufresnii, in which the ornamentation of the genital and 

 anal plates is totally different ; the median abactinal part of the bare inter- 

 ambulacral space is often somewhat depressed. The color of the test of dried 

 specimens is grayish, with a purple tinge, or frequently light pink, with 

 angular markings along the median interambulacral line, on the lower part 

 of the coronal plates, extending from the apical system to the ambitus. 

 Alive the color is dark violet, with a somewhat lighter background to the 

 bare median interambulacral space. 



Panama ; Gulf of California. 



PODOCIDARIS. 



Podocidaris A. Ag., 1869, Bull. M. C. Z., I. 

 (See Part II. p. 269.) 



Podocidaris sculpta 



! Podocidaris sculpta A. Ag., 1869, Bull. M, C. Z., I. 

 (See Part II. p. 269.) 



PI IV. f. 8-16. 

 Straits of Florida. 



