ECHINOIDEA. I. 153 



Echimis rarispbius G. O. Sars. 

 — iiiicrostonia W>\'. Thoms. 



Principal literature: Diiben «S: Koren: Ofvers. af Skandinaviens Echinodermer. p. 266, 268. — 

 M. Sars: Norges Echinodermer. p. 92. Middelhavets Littoral-Fanna. p. iii. — G. O. Sars: Nye Echino- 

 dermer fra den norske Kyst (Vidensk. Selsk. Forhandl. Kristiania. 1871. p. 23). Bidrag til Knndskaben 

 om Dyrelivet paa vore Havbanker. Ibid. 1872. p. 104. — Agassiz: Revision of Echini. p. 296, 489. 

 6. p. 77. Blake Echini (9). p. 39. — Wyv. Thomson: Porcupine Echinoidea (395). p. 744. — 

 Danielssen: Echinida. Nonske Nordh. Exped. (iio). p. 3. — E. v. Marenzeller: 269. p. 13. 270. p. 20. 

 — Koehler: 217. p. 121. Notes échinologiqnes (221). p. 20. 229. p. 23. — Pronho: 327. p. 8. — Hoyle: 

 Revised List of Brit. Echinoidea (202). p. 413, 415. — Bell: Catalogne of Brit. Echinoderms. p. 146— 49. 

 With regard to the other literature the reader is referred to Revison of Echini , Bell' s Catalogue , 

 and Ludwig's <-Die Echinodermen des Mittehneeres (256). 



This species, I think, is the one that has caused most difficulties to the systematists. As 

 shown by the synonyms enumerated above, a whole series of species has been established on more or 

 less distinct forms of it; some of these, however, are now commonly regarded as synonyms, while 

 others (norvegictts, iiiicrostonia, and partly Flciniiigii) are constantly mentioned as independent species, 

 although expressions as critical species* (Wyv. Thomson. Op. cit), it seems almost hopeless to 

 attempt to distinguish the species of Echinus known as E. rlrgaiis^), E. iiorvcgicus , E. iiiclo^ and E. 

 Flemingii (Agassiz 9. p. 39) sufficiently show the difficulty of distinguishing between them. The 

 best fonnded of these species is, no doubt, norvegicus, and so long as I had only examined the material 

 from the Ingolf -Expedition, and what was otherwise foinid in onr mnsenm of this form, I also 

 felt persuaded that it was a distinct species. After having collected a considerable material at the 

 Faroe Islands during the summer of 1899, and especially after having received a considerable number of 

 specimens of all sizes from the Mediterranean from Prof. E. v. Marenzeller, I have got to the result, 

 however, that the whole can only be interpreted as one very varying species, among the nnmerons 

 forms of which three tolerablv distinct varieties ma}', however, be distinguished: var. iiicth'frrratira, 

 Flemingii, and iiorvcgiciis. 



The northeru specimens are generally easily referred to respectively iiorvegicus or Fleiiiiiigir, 

 especially it seems that at the Norwegian coasts specimens are rather seldom found, which are only 

 with difficulty decidedly to be referred to one or the other of the mentioned forms. Most of the men- 

 tioned specimens from the Faroe Islands, on the other hånd, it was impossible with certainty to refer 

 to one or the other variet}'. In the Mediterranean a third, ven- large form occurs, which I have called 

 var. mediter raiica\ it does not seem to be found in the northern Atlantic, but in return var. Flemingii 

 is apparentlv not found in the Mediterranean. On the other hånd var. norvegiciis occurs in both seas. 

 ^ut in the Mediterranean this latter scarceh- occurs as a marked \ariety; in the material received 

 from Prof. v. Marenzeller, at all events, all possible transitions were found between the genuine iior- 

 vegicus and var. iiiediterraiiea. In the first of the essays quoted above v. Marenzeller has referred 

 the specimens before hini to E. norvegiciis after a comparison with northern specimens of this form; 

 in the latter he has, on the basis of a greater material, referred the whole to Ech. aciitus. I must 

 I) That E. elegans is mentioned in this connection is owing to a wrong interpretation of this species (conip. pp. 99, 1451, 



The In^olf-Expedition. IV. I. 20 



