ECHINOIDEA. I. 



153 



Echinus rarispiiius G. O. Sars. 



microstoma Wyv. Thoms. 



Principal literature: Diiben & Koren: Ofvers. af Skandinaviens Echinodermer. p. 266, 268. 

 M. Sars: Norges Echinodermer. p. 92. Middelhavets Littoral-Fauna, p.m. -- G. O. Sars: Nye Echino- 

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

 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. Norske Nordh. Exped. (no), p. 3. -- E. v. Marenzeller: 269. p. 13. 270. p. 20. 

 - Koehler: 217. p. 121. Notes echinologiques (221). p. 20. 229. p. 23. -- Prouho: 327. p. 8. -- Hoyle: 

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

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

 and Lud wig's Die Echmodermen des Mittelmeeres* (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 (norvegicus, microstoma, and partly Flemingii} 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. clegans*}, E. norvegicus, E. melo, and E. 

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

 best founded 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 found in our museum 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 numerous 

 forms of which three tolerably distinct varieties may, however, be distinguished: var. tncditerranea, 

 l-'lrmingii, and norvegicus. 



The northern specimens are generally easily referred to respectively norvegicus or Flemingii; 

 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 hand, it was impossible with certainty to refer 

 to one or the other variety. In the Mediterranean a third, very large form occurs, which I have called 

 var. mediterranea; it does not seem to be found in the northern Atlantic, but in return var. Flemingii 

 is apparently not found in the Mediterranean. On the other hand var. norvegicus occurs in both seas. 

 But in the Mediterranean this latter scarcely occurs as a marked variety; in the material received 

 from Prof. v. Marenzeller, at all events, all possible transitions were found between the genuine nor- 

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

 the specimens before him to E. norvegicus 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. acntus. I must 



') That E. elegans is mentioned in this connection is owing to a wrong interpretation of this species (conip. pp. 99. 145). 

 The Ingolf-Expedition. IV. i. 2 O 



