296 MR. F. P. BEDFORD ON MALAYAN" ECHIXODERMS. [Mar. 20, 



Oreaster nodulosus, F. J. Bell, Proc. Zool. Soc'1884, p. 66. 

 Reference, v. Marteus, Archie fiir N.aturg. 1866, p. 77. 



Locality. This species is found not uncommonly in about a 

 fathom of water on the shore of the lagoon off the east side of 

 Singapore Island. 



Distribution. Indian Ocean, Eastern Archipelago, and N. Aus- 

 tralia. 



The systematic classification of the genus Pentaceros offers 

 similar difficulties to those found in the Echinoid Diadema ; in 

 both cases we have exceedingly variable groups of individuals in 

 which the norm of the variations is different in different localities. 

 The four " species " Pentaceros turritus M. & T., P. hiulcus M. & T., 

 P. muricatus Gray, and P. alveola tiis Perrier, which Professor Bell 

 describes as " apparently distinct," are based on characters which 

 are admittedly subject to very great variation ; and while Prof. Bell 

 instances the presence or absence of marginal spines as a cha- 

 racter by which " we can always safely discriminate between 

 0. UncJci (=P. muricatus) and 0. nodosus ( = P. turritus) ,, (loc. cit. 

 p. 59), at the same time Dr. Martens- had named two varieties of 

 P. muricatus (var. mutica and var. intermedia) in which the marginal 

 spines completely fail : this of course is entirely due to the fact 

 that no two observers are agreed as to the best set of characters 

 to select for specific diagnoses, and in consequence a totally 

 different grouping of the same series of specimens would be re- 

 sorted to by different systematists. Whether it is advisable in such 

 a case to unite all the forms under one specific name, as has been 

 suggested for the Pacific Diademas by Prof. Loven, I do not feel 

 in the least competent to express an opinion. 



Specimens both with and without a central apical tubercle occur 

 at Singapore as elsewhere, and in the former case the apical 

 tubercles may be much longer and sharper than in the latter, 

 in which they are usually mamilliform ; I do not know if indi- 

 viduals with the marginal spines developed occur in the locality. 



Two specimens gave the following measurements : — 



R (act. side) = 116 mm., r=46; arm-breadth = 54 ; no. of inarg. 

 plates =23 ; 9 lophial tubercles, 3 or 4 interradials. 



R (act. side) = 128 mm., >- = 52 ; arm-breadth =58 ; no. of marg. 

 plates=27; 7 or 8 lophial tubercles, 4 interradials. 



13. CULCITA NOV^-GUINE^E, Var. ARENOSA. 



Culcita novce-yuinece, Miiller & Troschel, Syst. d. Ast. 1842, 

 p. 38. 



Culcita arenosa, J. O. E. Perrier, Revision des Stellerides, 1875, 

 p. 264. 



References. C. Ph. Sluiter, Natuurk. Tijd. v. Ned. Ind. xlviii. 

 1889, p. 305 (C. schmideliana). CI. Hartlaub, Notes from 

 the Ley den Museum, xiv. 1892, p. 65. R. Koehler, Mem. 

 Soc. Zool. Prance, viii. 1895, p. 388. L. Doederlein, 

 Semon's Zool. Forsch. in Austr. &c. Bd. v. Lf. 3, 1896. 



