milNOHKUMA. 9 



margin very sharp, the inner artiiml ambulacrals with spines, the oral angle provided 

 with a large spine. While the specific characters would appear to lie that the IOIIL'T 

 nulius is nnm- than twice as long as the shorter ratlins, the marginal plates arc very 

 numerous, and the innermost amlmlacral spine is spatulatc and fluted at ita free end. 



The smallest specimen has not quite acquired the generic characters of the larger ; 

 the abactinal integument is not so thick as to altogether hide the superficial granules, 

 and the granules on the actiual internmbulacra have not developed into spines, so that 

 t lii-re is no marked difference between the outer and the inner parts of these areas. 



PKXTAOONASTKR INCERTTS. 



The single small specimen, is, I think, an ally of the Australian species of Penta- 

 gonattter (sens, lot.), but the arms are proportionately longer than they generally arc 

 in this genus ; it is, possibly, an immature specimen in which It would gradually 

 increase in proportion to r. If it should prove to )>c an adult, its proportions may l- 

 compared to those of P. duetx-ni and /'. yunni; it is, however, to IHJ distinguished by 

 the fact that there are no large plates on the actinal inter-radial areas, the plates being 

 of the character of, and a little larger than, the small squarish granular plates which 

 bound the marginals; these last number about 12/14 for the side of each arm, and 

 are completed by a large terminal ; there are two rows of well-developed spines at the 

 sides of the ambulacra ; those of the inner row are nearly twice as long and as 

 numerous as the outer. I propose to call this form Pentagonaster incertus ; it was 

 taken at 96-120 fins., in MacMurdo Bay. 



LEPTOPTYCHASTER KERUUELENENSIS. 



Lf/tfoptycfuuter kfrgtulenmsu, E. A. Smith, Phil. Trans. lf.8 (1879), p. i'7s. pi. xvii. 2; Sladen, Chall. 



Rep. Ast. (I** li). p. 18t; Bell, Mar. Invert. 8. Africa iii. (l0. r >) p. 2L'. 

 Leptoptyfhaster antarctic UK, Sluden, op. eil. p. 190. 



I must own to some temerity in associating a specimen in which R = 212 and 

 r = 58 with a species whose type had /? = 38 and / = 12*5, and a representative 

 of which, hardly much larger, was found to be bearing young ; but even the most 

 recent writers on Echinoderras have not yet promulgated the doctrine that difference 

 in size is a specific character, though I am riot quite sure that in practice they do 

 not sometimes act as though they had. However, one has only to get a clear idea 

 of the essential characters of this genus to feel sure that one has it here ; as to spo ifi.- 

 characters, it is first to l>e said that most of the L. kerguelenensi* material is badly 

 preserved, while the condition of L. antarcticus is particularly good. Though the 

 differences between the two species appear, from Mr. Sladen's lengthy description, to 

 ! considerable, it will, I think, be found on examination of the specimens preserved 

 in the Museum, that L. antarcticus is but the expression of some early stages of 

 L. kergueleiicnsis. It will Ixj rememl>ered that both "species" come from closely 

 adjacent localities. At any rate, we now know that the specimens of L, antarcticu* 



