82 



Seychelles and from Hololhurian Bank are almost white; the spines are less 

 thickened at the point than in the typical form; the pits between the ocular and 

 the genital plates are very distinct, and the genital plates bear several tubercles 

 along their inner edge, forming a circle round the periproct. Perhaps the secon- 

 dary tubercles are also a little more numerous than in the typical form. In the 

 specimen from Torres Strait the secondary tubercles are distinctly more numerous. 

 These are, however, very trifling and unreliable différences, so that I find it necessary 

 to regard them all as belonging to one species. Only one form I must regard as 

 a distinct variety. It is beautifully red coloured, both on the test and spines, and 

 thus looks very different from the typical siamensis. I am, however, unable to find 

 other characters than the colour by which it can be distinguished from that species, 

 and the colour sometimes is little intense. The anal opening may be subcentral. 

 This variety, which I may name var. pulchellns, n. var., I have seen from the Ami- 

 rante-Islands and from the Maldive-Islands; further it was found in the „Siboga"- 

 collection, from the Stations: 43, 104 and 240. 



The genus Pleurechinus proves to be represented by a considerable number 

 of species in the Indo-pacific Ocean. Untill recently only the one species PI. 

 bothryoides was known, and it was considered a great rarity. In 1885 Döderlein 

 (in his paper „Seeigel von Japan und den Liu-Kiu-Inseln") described two new 

 species, PL ruber and variabilis. Bell (Echinoderms of Macclesfield Bank. 1894. 

 p. 410) points out that PI. bothryoides now has been shown to be „by no means a 

 rare species" — but as to the species described by Döderlein he has „a pretty 

 strong conviction that the progress of research will result in showing that Pleur- 

 echinus variabilis and P. ruber of Dr. Döderlein are synonyms of this variable 

 species". In his recent work on the Echinoidea from Amboina and Thursday Is- 

 land (Semens Reisen) (p. 705) Döderlein maintains his species against Bell, and 

 with full right. I have examined the type specimens of all the three species 

 hitherto described, as well as the specimens from Macclesfield Bank determined by 

 Bell as PI. bothryoides, and I find PI. ruber to be a very distinct species, whereas 

 PI. variabilis is so far from being synonymous with PI. bothryoides that it cannot 

 even be retained in the same genus; it belongs to the genus Opechinus Desor, 

 hitherto known only as fossil. The specimens from Macclesfield Bank are not PI. 

 bothryoides either but a distinct species, described below as PI. maculatus n. sp. In 

 the collections of the British Museum I have further found a number of small 

 specimens of Pleurechinus, identified as young Temnopleurus or even as Temno- 

 pleurus toreumaticus. As I could not examine all these specimens sufficiently during 

 my visit at the British Museum, Prof. Bell kindly sent me the whole material to 

 Copenhagen. By the close examination of these specimens they were found to 

 belong to three different species of Pleurechinus, viz. the above named PI. maculatus, 

 siamensis, and one species more which has proved to be identical with the „Temn- 

 echinus" scillœ, described by Mazzetti. Further the Copenhagen-Museum possesses 



