17 



the whole Indo-pacific region. In the Gulf of Siani and al Singapore, however, it 

 does not seem to occur. 



Besides Ü. antillariim and Savignyi Agassi/ further names D. globiilosum Ag., 

 paucispinum Ag. and nudum Ag. as synonyms of D. saxatile (setosum). Of 0. 

 globulosum there is an authentic specimen in the Museum of Copenhagen, received 

 from Agassiz (Society Islands). It is not the same species as saxatile. The large 

 tridentate pedicellariæ (head 1mm.) have broad valves (PI. III. Fig. 7.). Very slight 

 traces of dark impressions are found on the genital plates. The uppermost tubercle of 

 the inner interambulacral row is found on the fifth plate from above. The specimen 

 in hand is in no way more globular than specimens of D. saxatile of a corresponding 

 size, so that the form of the test will not give any reliable difference; and I 

 cannot decide from the single small specimen in hand, if other distinguishing cha- 

 raracters exist in the struture of the test. Spicules as in D. saxatile. — Possibly 

 this form will prove to be a distinct species, but for the present I must regard it 

 as synonymous with D. Savignyi. — Of D. paucispinum we have likewise an authentic 

 specimen (from the Sandwich Islands), but unfortunately it has been denuded, so that 

 I have not been able to examine its pedicellariæ and spicules. I think it certain, 

 however, that it is not synonymous with D. saxatile, on account of its small apical 

 system, the small naked interambulacral spaces and the absence of dark impressions 

 on the genital plates. Probably it is also synonymous with D. Sawz^/iy/. — D. nudum I 

 do not know, and from the description') nothing at all can be inferred with regard 

 to its true place. — As for D. Lamarckii Rouss. I must state, after having examined 

 the type specimen in Paris, that it is really identical with D. saxatile. 



The Sarasins") mention a form of Diadema from Ceylon, which they take 

 to be distinct from saxatile. It has a black analtube, and the blue spots are „in 

 Reihen zusammengeschmolzen, so dass die Interambulacra an Stelle der blauen 

 Fleckenreihen mit continuirlichen blauen Bändern geschmückt erscheinen". Evidently 

 this form is no üiadema at all but an Echinothrix (diadema{9)), as appears from the 

 numerous small ambulacral tubercles {Op. cit. Taf. III. Fig. 16). Also v. Uexküll ') 

 mentions „zwei Arten \on Diadema", which he has used for his experiments in Dar-es- 

 Salaam. But he does not give any information as to the differences between these two 

 species. As he likewise mentions a species of Echinothrix and one of Astropyga, it 

 cannot well be supposed that his second species of Diadema belongs to a different 

 genus. Probably v. Uexküli.'s two species of Diadema from Dar-es-Salaam are D. 

 saxatile and Savignyi, which seems to indicate, that the two species are easily 

 distinguished in the living state. 



') Synopsis of the Echinoidea collected bj' Dr. W. Stimpson on tlie North Pacific Exploring Expe- 

 dition. Proc. Acad. Nat. Sc. Philadelphia. 1863. p. 353. 



') Ergebnisse naturwiss. Forschungen auf Ceylon. 1. Die Augen und das Integument der Diade- 

 matiden. 1887. p. 5. (Taf. Ill, 16). 



') Die Wirkung von Licht und Schatten auf die Seeigel. Zeitschr. f. Biologie. 4(J. 1900. p. 448. 



L). K, U. Vklensk. Scisk Skr., 7. Hiukkc, nutur\'iilensk. oj; inathem. Aid. II. 3 



