BCHINOIDEA. II. IO g 



sur les Ech. Pl.XII.io2, XXXI. On Pourtalesia PI.X.100. - Bell: Catalogue Brit. Ech. p. 164. — 

 Hoyle: Revised List Brit. Ech. p.422. — Koehler: Note prelim, sur les Echinides, Ophiures et Cri- 

 noidees rec. en 1S9S— 99, «Princesse Alice . Bull. Soa Zool. de Fr. 1901. p.99. Grieg: Nordlige Norges 

 Echinodermer. p. 32. -- Doderlein: Echiuoiden d. deutschen Tiefsee-Expedition. p. 253. Taf. L. Fig. 2. 

 — Fauna Arctica. Seeigel. p. 385. 



For other less important literary references see Rev. of Ech. and Hell's Catalogue. 



This species is very well described by Diiben and Korea and later on by Agassi/., so that 

 very little remains to be added as regards the structure of the test. — 



The shape of the test is rather variable; sometimes it is more rounded, sometimes more elongated; 

 not seldom it is unequally developed, the right side projecting beyond the left in front, though somewhat 

 less than is generally the case in Spatangus purpureus. -- In Revision of Ech.- PI. XXI. 3 is figured 

 a specimen in which the left side projects beyond the right. There can, however, scarcely be any 

 doubt that this figure (photograph) has been reproduced in inverted position; this is especially shown 

 by the genital pores: in this figure there are two genital pores on the right side, whereas they are 

 really found on the left side, as stated by Agassiz himself, Rev. of Ech. p. 263 — : «three genital 

 openings, right anterior obliterated*. -- (A similar inverted reproduction is found in the «Hassler»- 

 Echinoidea. PL II. 4, Nacospatajigus gracilis, and, probably, PI. IV. 6, 8, Hemiaster Philippii). — The 

 height of the test likewise is rather variable, especially the abactiual keel formed by the posterior 

 interambulacrum may differ very much, being sometimes quite indistinct, sometimes very prominent. 



The length of the posterior petals is generally scarcely one third of that of the anterior ones; 

 in a specimen from Bergen, however, they are more than half as long as the anterior ones, and the 

 apical system in this specimen is subcentral, whereas the apical system is otherwise near the posterior 

 end. (This specimen is figured in PI. I. Fig. 7, the Fig. 6 showing a normal specimen of the same size 

 for comparison). In the same specimen the posterior part of the labrum is longer than usual, reaching 

 to the 2. ambulacral plate on one side, to the posterior edge of the 1. ambulacral plate on the other 

 side, whereas it normally ends off the middle of the 1. ambulacral plate. Also the plastron is broader 

 than usual. Upon the whole this specimen differs very considerably from the typical form and 

 would undoubtedly have been made the type of a distinct species, had it come from a more distant, 

 less well known locality; but, as the Norwegian specimens otherwise do not show these characters, 

 such a single specimen can certainly only be regarded as an abnormal, probably atavistic case. But it 

 might well be worth looking out for similar specimens — as, of course, the existence of another species 

 of Scliizastcr in these regions, cannot be declared impossible. — Evidently the specimen of which 

 Grieg (Op. cit.) gives some measurements has some resemblance to the above mentioned, though the 

 posterior petals are not so long as here. 



According to the statements of Agassiz ( Blake -Ech. p. 74) there is considerable variation in 

 the distinctness of the lateral fasciole as it passes under the anal system. In some cases it stops sud- 

 denly near the level of the anal system; in others it can be faintly traced as an indistinct, irregular 

 anal fasciole; in others the anal fasciole is most clearly marked. These differences do not depend on 

 size, but specimens from one locality are usually similarly affected-. Under the description of Schizaster 

 orbignyanus ( Blake»-Ech. p. 76) Agassiz further says: «It is interesting to note that in the specimens 



