123 



by Bell (Op. cit. PI. XXVI. Fig. 3) Ihe poriferous zone looks very peculiar, the pores 

 being arranged in sets of two, and the porebearing plates being separated from the 

 inner part of the ambulacral plate. This is wrongly drawn; the ambulacra are 

 quite typically echinoid, with the pores arranged in distinct arcs of three. 



„It is a somewhat difficult matter to suggest what are the nearest allies of 

 this species", says Bell. I think Ihere can be no doubt that it is nearest allied to 

 verruculatus among the Psammechiniis-species, whicli species has likewise only small 

 plates in the buccal membrane, though larger than in Ps. rufus, both differing in 

 this respect very much from Ps. variegatiis, where the buccal membrane is quite 

 covered by thick plates. But on the oilier hand Ps. rufus reminds one of the Gijmn- 

 ec/i/nus-species, especially of G. pulcheUus, in which species a few small fenestrated 

 plates may occur in the buccal membrane outside the buccal plates. Also tlie 

 rather excentric periproct of Ps. rufus reminds one of the Gymnec/ifnus-species of 

 Ihe Robillardi-group. It seems thus that Ps. rufus forms the transition from Psamm- 

 ecliinus to Gymnechinus, and it might almost as well be referred to the latter genus; 

 but it is most practical to refer it to Psammechinus, as otherwise the limits of these 

 two genera would become indistinct — and these two genera must be maintained, 

 as it would be rather absurd to unite the extreme forms, Ps. variegatus and G. 

 Robillardi or versicolor into one genus. 



In the collection of Echinids sent me from Prof. Harmeh (here are several speci- 

 mens (naked tests) of Psammechinus verruculatus from the Sandwich Islands, which 

 are peculiar by having the pore-areas and the adjoining part of the interambulacra 

 (outside the primary tubercles) beautifully red coloured ; also the usual greenish 

 spots are found. On a specimen from Samoa (Hamburg Museum) preserved in 

 alcohol, it is seen that the spines are white, with 1 — 4 narrow, red bands. In spite 

 of this characteristic coloration this beautiful form can scarcely be regarded as distinct 

 from verruculatus, no other differences being found. And among tlie specimens 

 from the Sandwich-Islands there are some with the red colour faintly indicated and 

 others without any indication of it. In one specimen with a few spines preserved 

 these are violet at the base. — According to de Loriol (Echinod. Maurice, p. 23) 

 two ocular plates reach the periproct; this is the case in some of the specimens 

 before me, in others, however, only one ocular plate reaches the periproct. 



De Meliere (,,Siboga"-Echinoidea p. 101) expresses his doubt ot Echinometra 

 oblonga being a distinct species, as he finds all transitional forms between £. Matthœi 

 and oblonga. In the „ Ingolf "-Echinoidea (p. 129) I have stated that E. oblonga agrees 

 with the other species (lucunter etc.) as regards spicules and pedicellariæ, mention- 

 ing only that it has a joint on the stalk of the globiferous pedicellariæ. In a letter 

 to me Prof. Döderlein has called my attention to the fact that the Echinometra 

 oblonga has, indeed, triradiate, not bihamate spicules in its tubefeet. My statement, 

 that it has bihamate spicules, was occasioned by my having relied upon a 

 determination of Lütken. It was not my intention to work out more closely the 



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