354 PROCEEDINGS OF THE ACADEMY OP 



ciently with the figure of Rumphius of D. setosum, PI. 14, fig. 5, to show that 

 they belong to the same genus, I find that it is an entirely different genus, 

 which have I named Echinostrephus, Bull. Mus. Comp. Zool., 1863. The 

 figure of Leske, PI. 37, figs. 1, 2, which is also always quoted as D. turca- 

 rum, is a true Diadema, probably identical with the species which I have called 

 D. nudum. The D. turcarum, or the Echinothrix turcarum of Peters, is a 

 Garelia, and not Echinothrix, Peters having included in his genus Echinothrix, 

 several species which had already been separated by Gray as a distinct genus 

 from Diadema, Garelia. The Echinothrix turcarum Pet. may prove identical 

 with the Garelia cincta, mentioned above, but as I have no specimens, and only 

 the figure of Rumphius, I am unable to decide this point. 



"Body everywhere, spines included, of a purplish black color. Soft parts 

 bluish grey. Anus margined with light blue." 



" Hong Kong, China, in crevices of rocks, 1 fathom." 



"Island of Ousima, below 1. w. m." (W, Stimpson.) 



THRICHODIADEMA A. Ag. 



Ambulacra of a true Diadema ; pores arranged in irregularVertical arcs of 

 three pairs of pores ; not spreading near the actinal region. Two rows of 

 large tubercles in the ambulacral space. Interambulacral area with two 

 vertical rows of large tubercles extending from the mouth to the abactinal 

 region ; on each side of these rows tubercles smaller than the ambulacral, ar- 

 ranged in vertical rows and not in oblique rows, as is usual in the Diadema- 

 tidae. Abactinal system almost circular, which distinguishes this genus 

 at once from all other known genera of this family. Shell thick ; tubercles 

 crenulated ; spines resembling those of Echinothrix, but stouter and more taper- 

 ing. 



THRICHODIADEMA RoDGERSII A. Ag. 



Tubercles of ambulacra crowded together with a double zig-zag row of small 

 miliary tubercles. Tubercles of interambulacral area arranged in eight ver- 

 tical rows. Anal membrane small, covered with minute elliptical plates. The 

 verticillations of the spines very close ; whorls arranged in such a way that 

 the surface of the spines appear longitudinally striated. Outline seen from 

 above perfectly circular, regularly arched when seen in profile. 



"Taken in clefts of rock at 1. w. m. in Port Jackson, N. S. W. Color of a 

 deep reddish purple." (W. Stimpson.) 



Hkterocentrotos mammillatus Br., Prod. 



Dr. Stimpson had the good fortune to find at the Bonin Islands a number of 

 specimens of a species of Heterocentrotus, which are undoubtedly the H. Pos- 

 tellii of Brandt. After carefully comparing the specimens with the originals 

 of Acrocladia haslifera Ag., A. mammillata Ag., I have satisfied myself that the 

 different species which have been distinguished principally by means of the 

 great differences in the spines, are simply individual differences. The pecu- 

 liar mode of growth of the spines by concentric longitudinal layers, giving 

 rise in different specimens to bat-shaped, triangular, cylindrical or club- 

 shaped spines. In specimens in which the spines have been broken and 

 have grown out again afterwards, we find the best proof of the identity of 

 these different modes of growth. 



"Bonin Islands and Hilo, Hawaii." (W. Stimpson.) 



Podophora Quoyi A. Ag., Bull. Mus. Comp. Zool. 1863. 

 " Hilo, Hawaii." (W. Stimpson.) 



Colobocentrotus Leskei Br. Prod. 



" Black above, dark reddish brown below; a circle of bright red around 

 the mouth. On surf-washed rocks in 4th 1., Port Lloyd, Bonin Islands." 

 (W. Stimpson.) 



[Deo. 





