282 BULLETIN OF THE 



Echinus Flemingii Ball, Forbes Brit. Surf. 



Among the Echini dredged by Mr. Pourtales is a single small specimen 

 which I am unable to distinguish from specimens of the same size of E. 

 Flemingii. It may be that, when more extensive series of the young of 

 E. melo, E. Flemingii, anil E. gracilis, described above, have been com- 

 pared, that we shall find these species to be only local varieties, though I 

 am not inclined, from the material at my command, which is quite ample, 

 to adopt this view, but rather suppose that we have here, side by side, two 

 allied species, one of which has an extensive range. Grube already con- 

 siders E. melo and E. Flemingii as identical ; I suspect he has only found 

 the two species side by side, as they are both known to inhabit the Medi- 

 terranean. 



In 195 fathoms. 



Genocidaris maculata A. Ao., nov. gen. et sp. 



This genus is established for a small Sea-urchin, the living representative 

 of Opechinus, which Desor separated from Temnopleurus. The spines 

 resemble in their structure those of Temnopleurus, but are short ; the 

 Sea-urchin with its spines resembling a Psainmechinus, and having, like 

 it, a large number of tubercles, of nearly uniform size, closely crowded 

 together, but of a peculiar chiselled structure (so that it may be said that 

 this genus is a Psammechinus among Temnopleur'uke), there is one principal 

 row in the ambulacral and interambulacral area larger than the others. The 

 poriferous zone is narrow ; the pores are arranged in an unbroken vertical 

 row separated by an arched ridge. The mamelon of the primary tuber- 

 cles is smooth, imperforate. Near the base of the tubercle the test is orna- 

 mented by cuts specially marked near the suture of the plates, and the 

 small tubercles are frequently connected by a ridge with the main tuber- 

 cles, the ridge forming spokes radiating from a hub, similar to the structure 

 of Glyphocyphus radiatus, and some species of Ecb.inocypb.us. The genera 

 Opechinus, Temnotrema, Trigonocidaris, and Genocidaris form a transition 

 between Psammechinus and Temnopleurus. The actinal membrane is bare, 

 with the exception of the ten small circular buccal plates. The actinal 

 opening is not large, with slight indentations ; the test is irregularly covered 

 will) pedicellariaj, having a blunt head surmounting a long, slender stem, 

 articulating upon a shorter, stout rod. The abactinal system is peculiar, as 

 we find, in the largest specimens even, which appear fully developed, but 

 a single circular plate, slightly conical, occupying nearly the whole anal 

 system, with the exception of a small crescent-shaped slit, covered by four 

 very small plates. This genital plates arc large pentagonal, with a deep 

 groove, in which is situated the genital opening, having on the anal edge a 



