lo8 ECHINOIDEA. II. 



Figs. 1—4) as Pcriasfer Umicola' . I quite agree witli the eminent anthor herein, and having examined 

 the specimens in the Britisli Museum I am able to add some more differences to tliose now found by 

 Professor Agassiz between the vChalleuger^' specimens and the true P. Umicola. The labrum ends 

 off the first adjoining ambulacral piates. There are four large snbanal tube-feet. One specimen has 

 two genital pores, the other has four, the two anterior being quite small. The latero-anal fasciole has 

 quite disajjpeared in one specimen, in the other there are distinct traces of it The froutal tube-feet have 

 a well developed disk, strongly lobate in the edge, the rosette-plates reaching only the beginning of the 

 lobes. The spicules are very unmerons, rather mnch brauched, otherwise like those of li)incola. The 

 globiferous pedicellariæ are of the Schizasterid type, with a very large space within the blade (PI. XIV. 

 P'igs. 1,4); there is one tooth ou either side ot the terminal opening. The stalk has a limb above, where 

 the niuscles from the head are fastened, and a small ring below. The tridentate pedicellariæ (PI. XIV. 

 Fig. 21) are rather similar to those of P. Ihiiicola, viz. the slender form. The long and slender valves 

 join only at the point; the edge is in the lower jjart very coarsely and irregularly serrate; there is 

 a little meshwork, sometimes rather coarse, in the blade. Rostrate pedicellariæ have not beeu found; 

 the ophicephalous pedicellariæ (PL XIV. Figs. 5, 36) are of the usual Spatangoid type, and there is a 

 prolongation from the lowermost of the arcs. The stalk is not distinctly cnpshaped above. The tri- 

 phyllous pedicellariæ do not present peculiar features. 



The differences pointed out by Professor Agassiz and liere, together with the geographical 

 distribution: one a deep-sea form from the Gulf of Mexico, the other a littoral form from the Arafura 

 Sea, leave no doubt that this is another species; if it be a new species is not so certain. It is very 

 like the Scliizasfcr Jiikesii Gray both in the characters of the test and of the pedicellariæ, and even 

 the locality is the same; indeed, I think it almost beyond doubt that it is really identical with that 

 species. — (In ^Revision of Echini?' Scliicastcr fnkcsii is made a synonym of Sch. vcntricosus (lacu- 

 tiosiis L.); this is, however, certainly not correct; the verification thereof will be given in Part II of 

 the Siam-Echinoidea). Whether Schizastcr Jtikcsii ought really be reckoned to the genus Periastcr, as 

 is done, in faet, by Agassiz in the > Challenger»-Echinoidea, is not easy to determine, these genera 

 being upon the whole very closely related. Perhaps the globiferous pedicellariæ may indicate the 

 correctness of referring Sch. Jukcsii to Periastcr ; in any case they differ considerably from those of 

 Schizastcr lacitiiosns a. o. (comp. bclow). But upon the whole I do not venture to enter in a more 

 detailed mauner on a discussion of tlie rather difficnlt question of the genus Periastcr, my knowledge 

 of the fossil forms being too insufficient. 



27. Brisaster (Schizaster) fragilis (Diib. Kor.). 



PI. I. Figs. 6—7. PI. XIII. PI. XIV. Figs. 3, 7, 11, 13—16, iS, 20, 24—25, 31, 37, 39, 43, 46, 50—51. 

 Synonyms: Brissus fragilis Diib. Kor. 



Tripylus fragilis Sars. 



Principal literature: Dfiben & Koren: Skandinaviens Echinodermer. 1844. p. 280. Tab. X. 47 — 



49. — Gray: Catalogne Rec. Echinida. 1855. p. 61. — Liitken: Bidrag til Kundskab om Echiniderne. 



p. 175 (107). — Sars: Norges Echinodermer. p. 96. — Agassiz: Rev. of Echiui. p- 157, 363. PL XXI. 3, 



XXVI. 42. — «Challenger»-Echinoidea. p. 201, «Blake -Ech. p. 74. PL XXVIII. 8—14. — Loven: Etudes 



