107 



Agassiz thinks it possible that this species will prove to be „nothing but 

 H. porosissimiis with a rather narrow poriferous zone". It is a priori very impro- 

 bable that so large specimens as the type (53 mm.) should not yet have attained 

 the definitive arrangement of the pores, and the fact that in specimens of poro- 

 sissimtis of much smaller size the characters in the ambulacra are already very distinct 

 (comp, measurements below), definitely proves that it must be two distinct species. 



Holopneustes inflatus Ltk. The type-specimen is a naked test, only some 

 spines being preserved; they are clabshaped, of a faint reddish tint. In the British 

 Museum I have found some small specimens of this species from Port Philip 

 (named Ambl. ovum); they show that in pedicellariæ and spicules there is no dif- 

 ference from H. purpurascens. In the description of this species given by Agassiz 

 (Rev. of Ech. p. 483) it is said: „poriferous zone more than equalling in width the 

 median ambulacral region" ; as in H. purpurascens this means not the whole inter- 

 poriferous zone, but only half of it, the poriferous zone being only a little more than 

 half as wide as the median, non-poriferous part of the ambulacral area. A feature 

 worth mentioning for this species is this that the interambulacral plates make a 

 distinct curve downwards below the primary tubercle, most distinctly on the abac- 

 tinal side; in H. purpurascens this feature is very indistinct in the type-specimen, 

 but in the small specimen from Port Philip it is rather distinct, as is also gene- 

 rally the case in H. porosissimus. It may also be noted that the ambulacra are 

 only as wide as the interambulacra, whereas in H. porosissimus they are distinctly 

 wider than the interambulacra even in quite small specimens. By this feature H. 

 inflatus is easily distinguished from porosissimus, whereas it is difficult to distinguish 

 it from purpurascens. The test is higher in purpurascens and the whole form is dif- 

 ferent: in purpurascens the test is eggshaped, narrowing evenly towards the mouth, 

 whereas in inflatus the actinal side is rather broad and flat. Also the colour is 

 different, dark purplish red in purpurascens, faint reddish or brownish in inflatus 

 (both test and spines). Perhaps it will not be possible to maintain inflatus as a 

 distinct species ; there is in the Copenhagen Museum a large specimen from Victoria 

 (42 mm.) which seems to hold an intermediate position between purpurascens and 

 inflatus. But from the scanty material at my disposal I dare not say with certainty 

 whether inflatus has to be made synonymous with purpurascens or maintained as 

 a distinct species. The suggestion of Ramsay') respecting the three Holopneustes- 

 species that „it is quite likely that they all belong to one species" is undoubtedly 

 wrong and caused by his having confounded not only the species but also the 

 genera Amlilypneustes and Holopneustes (see above, sub. A. ovum); in any case the 

 two species purpurascens and porosissimus must be maintained. 



Holopneustes porosissimus Agass. The pedicellariæ are like those of H. pur- 

 purascens; the spines are strongly clubshaped and of a conspicuous red colour. I have 

 examined two young specimens from Port Philip; they agree with the larger spe- 

 ') Catalogue Ech. in the Au.stralian Museum. I. Echini. 1891. p. 52. 



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