ECHINOIDEA. II. joQ 



sur les Écli. PI. XII. 102, XXXI. — Ou Pourtalesia. PI. X. 100. — Bell: Catalogiie Brit. Ech. p. 164. — 

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

 noidées rec. en 1898—99, ;Princesse Alice >. Bull. Soc. Zool. de Fr. 1901. p.99. — Grieg: Nordlige Norges 

 Echinodermer. p. 32. — Doderlein: Echiiioiden d. deutscheu Tiefsee-Expedition. p. 253. Taf. L. Fig. 2. 

 — Fauna Arctica. Seeigel. p. 385. 



P"or otlier less important literar}' references see .Rev. of Ech. and Bell 's Catalogue. 



This species is very well described by Diiben and Kor en and later on by Agassiz, so that 

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



The shape of the test is rather variable; sometimes it is more rounded, sometinies 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 Spataiigns purpiirciis. — In Revision of Ech.- PL XXI. 3 is figured 

 a specimen in which the left side projects beyond the right. Tliere 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 tliere are two genital pores on the right side, whereas they are 

 really fonnd 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 fonnd in the «Hassler»- 

 Echinoidea. PI. II. 4, JVacospafaiigns gracilis, and, probably, PI. IV. 6, 8, Hciiiiastcr , Philippii). — The 

 lieight of the test likewi.se is rather variable, especially the abactinal keel formed by the posterior 

 interambulacrum may differ very ninch, 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 ajDical system is otherwise near the posterior 

 end. (This specimen is fignred in PI. I. F'ig. 7, the Fig. 6 showing a normal si^ecimen of the same size 

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

 to the 2. ambulacral plate on one side, to the posterior edge of the i. ambulacral j^late on the other 

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

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

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

 less well kuown localit)-; but, as the Norwegian .speciinens 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 Schizastcr in these regions, cannot be declared impossible. — Evideutly 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 liere. 



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 snd- 

 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 ^c^/zaj/^r 

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



