DOEOCIDARIS PAPILLATA. 255 



to Cape Sagras collected by the Porcupine Expedition, and which I owe 

 to Prof. Wyville Thomson, shows such astonishing variation in the propor- 

 tions of the coronal plates, the length and thickness of the spines, the posi- 

 tion and size of the genital openings, the size of the anal system, of the ocular 

 plates, that the differences I had supposed to be specific between C. papillata 

 and D. abyssicola can only be considered as amounting to individual vari- 

 ations. The difficulty of distinguishing the Mediterranean C. hystrix from 

 the northern C. papillata had already suggested their probable identity, and 

 now that we have the fine series of the Porcupine Expedition, we can hardly 

 hesitate to unite as one species Cidaris papillata, hystrix, abyssicola, and 

 affinis (or Stokesii) ; the latter being the name given to Mediterranean speci- 

 mens having comparatively shorter and more distinctly serrated spines than 

 is the case in specimens where the fluting of the spines becomes more promi- 

 nent, accompanied also by more slender papillae, features which are repeated 

 in the individual variations of specimens of one and the same locality in 

 the fine series of the Porcupine Expedition collections. It is true that the 

 color given by Philippi and Sars of C. affinis as brilliant vermilion is very 

 different from the color of the Florida specimens, which Mr. Pourtales informs 

 me are when alive more or less straw color, with a tendency to a dull green- 

 ish-brown color, quite well developed in some of the specimens ; but as color 

 forms such an unimportant feature in the specific characters of Echini, much 

 stress cannot be laid upon this point. 



Median interambulacral space sunken, vertical suture of plates distinctly 

 marked, edged by narrow bare space ; three to four concentric rows of sec- 

 ondary tubercles, but slightly smaller than those of the scrobicular circle, 

 extend towards median line from scrobicular circle. Scrobicular area sunken, 

 elliptical. Mamelon small, prominent; mammary boss small, indistinct. Broad 

 zone of secondary and miliaries separating the poriferous zone, the secondary 

 tubercles arranged in irregular radiating rows, separated by slightly marked 

 furrows. In the median ambulacra! region the two inner vertical rows of 

 secondary tubercles are near the middle and but little smaller than the ex- 

 ternal rows. Spines long, fluted, scarcely tapering, often equal in length 

 to twice the diameter of the test. From twelve to eighteen longitudinal fur- 

 rows on spines, frequently forming lamelke, or simply ridges with interstitial 

 space fully grown up ; collar of spine short, milled ring prominent, 



Abactinal system sparsely covered with miliaries in central part of plates, 

 leaving edges bare, well marked by a wavy double line of small tubercles. 



