KONGL. SV. VET. AKADEMIENS HANDL. BAND. 19. N:0 7. 73 



his notice, he doubtless would have referred it to Hemiaster Des. This became also 

 the view taken by Al. Agassiz, and since 1872 every author who mentioned these two 

 species, treated them as living representatives of that genus, thus associating them 

 with a höst of long known fossil forms that once peopled the seas of the Cretaceous 

 and Tertiary periods, and with their more lately added recent congeners, Hemiaster 

 expergitus Lov.^), discovered by Smitt and Ljungman during the cruize of the Jose- 

 phine in 1869, H. gibbosus Al. Ag. and H. zonatus Al. Ag., both dredged by the 

 Challenger Expedition^). Now these three species of the existing seas are true Hemi- 

 asters fully sharing the well-known characteristics of that highly natural genus, the sub- 

 globose form, elevated in its posterior region, a calyx of four costals, the madreporite 

 confined to the costal 2, the 4 and 1 and the radials I and V closing from either 

 side, in strict accordance with the mode of conformation universally prevalent within 

 the calvcinal system during the older Mesozoic period. These species are, as it were, 

 apparitions from a former world, relics surviving from an evolutional stage long pas- 

 sed tlirough, and very different from the altogether modern Abatus, with its modera- 

 tely convex test, its calyx with tive costals, the 5 being reproduced between the ra- 

 dials I and V and bearing the madreporic filter, thus set free, on its unimpeded retro- 

 grade movement. An extraneous form like this''), if suffered to remain in the other- 

 wise homogeneous group of true Hemiasters, is sure to vitiate its integrity, and the 

 mixed assemblage thus set up for a natural genus, if taken on trust, cannot fail to 

 mislead when the question is to trace out coniparatively its former geological and ac- 

 tual geographical distribution. The few survivors hitherto found of the once nume- 

 rous genus Hemiaster inhabit teraperate and tropical parts of the Atlantic and Pacific 

 oceans, the Caribbean and Brazilian Seas, through that of the Azores towards Madeira 

 and the Iberian peninsula, the Sea of Japan and that between New-Guinea and Austra- 

 lia. Abatus, on the other hand, is an antarctic form. 



1851. Faoi-iiin antarctioa Gray, Ann. Nat. Hist. 1. c. 132. 



1855. Gray, Cat. Br. Mus., 57. 



1876. Hemiaster cordatus Verbii.l Bull. Un. St. Nat. Mus. Wasliiugton, N:v 3, 68. 

 Hemiaster sp. 1876. Wvv. Thomson, Journ. Linn. Soc. XIII, 67. 



1877. Hemiaster Pliilippii »Grayu, Wyv, Tiiojison, Voy. Challeng:er, II, 227. 



Obs. Abatus cavernosus Phil. nppears to be the female, Ab. auslralis the inale. Gray' remarks, Cat. Br. 

 Mus. 57, that the three, Faorina antarctioa, cavernosa and australis, perhaps are only oiie species. Tripylus Phi- 

 li])pii Gray is generically different, probably an Agassizia, as also Tr. excavatus Phil. 



2. Abatus Philippii Loven. 



1871. Abatus Philippii Loven, Öfversigt af K. Vet.-Akad. Förhandl. N:r 8, 1065, 1070. 



1874. Loven, Études s. les Éohinoidées, pl. XI, fig. 99; pl. XXIX, f. 188—190. 

 Hemiaster » » 1873. Al. Agassiz, Bull. Mus. Comp. Zool. III, n:o 8, 189. 



1874. Al. Agassiz, Zool. Eesults Hasler Exp. I, 20. 

 Obs. The synonymy is doubtiul, because the sexual pores are said to be wnvo or three», and »if a third 

 exists it is the right anterior one, usually, bnt soraetiraes the left». 

 1) Études, p. 13, pl. Xin, fig. 114—120. 

 -) Eep. Chall. Ech., p. 184, pL XX, fig. 1—16. 

 ^) Another stranger is Hemiaster elongatus of Indian Tertinrios. It is a Palreostoma. 



K. Vet. Akad. Handl. B.ind 19. N:o 7. ' 10 



