2i(> Annals of the South African Museum. 



that it changes from a nearly pentagonal form, uniformly covered 

 with pseudopaxillae and minute rough spinules, with no large spine- 

 lets whatever', into a stellate form with moderately long rays, having 

 conspicuous spinelets on all adambulacral and marginal plates. 

 During this change pedicellariae are whollv lost, at least abactinallv. 



O / li 



It is worthy of special note that the large spinelet of the adambula- 

 cral plates appears first on the distal part of the ray and occurs 

 proximally only after the individual is half grown. The second set 

 of spinelets on the marginal plates appears only in what is apparently 

 the fully grown individual. 



DlPSACASTER SLADENI. 



Alcock, 1893. Ann. Mag. Nat. Hist. (6), vol. 11, p. 87; pi. 5,. figs. 3, 4. 



These specimens answer so well to Alcock's description that I feel 

 satisfied they should be referred to sladeni, but in two particulars 

 they are different; the pedicels of the paxillae are certainly not "long, 

 slender", as I understand those terms, and the adambulacral spines 

 are not what I should call "needle-like". Such terms ought not 

 however to be construed too rigidly. The adambulacral armature of 

 the South African specimens is almost exact lv like that of laetmophilus 

 Fisher, and the only point in Fisher's description to which the present 

 specimens do not answer is the covering of the infermnarginal plates, 

 in describing which Fisher uses the word "squamiform". There is 

 nothing "squamiform" in the spinelets covering the inferomarginals 

 of the African specimens. Comparison of Fisher's description and 

 figures of laetmophilus with Alcock's of sladeni certainly suggests the 

 identity of the two, but oddly enough Fisher makes no reference 

 whatever to sladeni. * 



The present series reveals some very interesting growth changes 

 in this starfish. The smallest specimens have R = 15 mm, and 

 r = 7, while the rays are nearly 10 mm. across at their very base ; 

 thus R = 2r and about 1-5 br. A somewhat larger specimen has 

 R = 26 mm., r = \\ and Ar 13; thus R = 2-36 r and 2 br. The 

 next larger specimen has R = 45 mm., r = 17 and br = 18; thus 



* After critical examination of the South African specimens of sladeni, Fisher 

 finds at least half a dozen differences between them and laetmophilus. Of these 

 the most obvious, if not the most important, is in the spinelets of the infero- 

 marginals, which are distinctly squamiform in the Alaskan species and spiculiform 

 in the African. Other important differences are to be found in the form of the 

 inferomarginals, in the plates and fasciolar channels of the actinal intermediate 

 areas, and in the mouth plates. The two species, although nearly allied, seem to 

 be perfectly distinct. 



