284 'lu- MOUTKNSEN. 



In my report on the Echinodernis of the Amdrup Expedition 

 ("Echinoderms from East Greenland". Medd. om Grønland. XXIX. 

 1903. p. 89) I have indicated Trochostoma boréale (Sars) as occurring 

 at East Greenland (Flemming Inlet, 118 fms., Angmagsalik, 140 fms.); 

 I followed Ludvig in regarding Tr. arcticum (Marenz.) with the 

 varieties parvum Théel and coeriilenm Théel as synonyms of that 

 species, Avithout having, however, studied the question more closely. 

 On studying the geographical distribution of the Echinoderms of 

 Greenland on the present occasion I was struck with the remarkable 

 distribution of this species. In "Fauna Arctica" (Holothurien p. 161) 

 Ludwig gives its distribution as follows: Florida Riff, Lesser An- 

 tilles, Portland (Maine); West of Norway, Finmark, Spitzbergen, Kara 

 Sea, Sibirian Ice Sea, Point Barrow. He remarks that "an diesem 

 Verbreitungsgebiete fällt auf, dass die Art an Grönland und Island 

 zu fehlen scheint". Gh. L. Edwards (The Holothurians of the 

 North Pacific Coast of North America collected by the Albatross in 

 1903. Proc. U. S. Nat. Museum. Vol. XXXIII. 1907. p. 53) gives the same 

 distribution of the species (under the name of Trochostoma oöliticum 

 (Pourtalès)), adding only a number of Pacific localities for it, so 

 that its range is considerably extended (to lat. 50° N., Vancouver Is- 

 land). Oster gren (The Holothurioidea of Northern Norway. Ber- 

 gens Mus. Årbog. 1902. p. 22) considers the species as arctic, remarking 

 only that it is "to be met with far to the south, down to the 12° N., but 

 onlv at great depths, where the water even within the tropics is cold". 



On zoogeographical grounds it seems very unlikely that the 

 specimens from Florida and the West Indies should be identical 

 with the purely arctic Tr. boréale or arcticum. It is true that other 

 Echinoderms widely distributed in the arctic seas, even circum- 

 polar, go far down to the South (Cribrella sanguinolenta, Ophiacantha 

 bidentata e.g.); but in such cases their distribution is continuous, w4iile 

 in the case of Trochostoma boréale the distribution is discontinuous, 

 the species being not known from Iceland, the Arctic East Coast of 

 Amerika, and at Greenland only from the East Coast. It was then 

 with great satisfaction, that I observed that H. Lym. Clark in his 

 great work "The Apodous Holothurians. A Monograph of the Synap- 

 tidæ and Molpadidæ" (Smiths. Contr. to Knowledge. XXXV. 1907) 

 had come to the result that both Tr. arcticum and the variety par- 

 vum Théel must be regarded as separate species. The genus Trocho- 

 stoma (together with /lnÄ-f/rof/er/7iü) being regarded as synonyms only 

 of Molpadia ( — in which I am inclined to agree with Clark — ),' 



' E. Hérouard in his paper "Sur les Molpadides de Norvège" (Bull. Inst. Océano- 

 graphique. No. 177. 1910) again maintains Trochostoma as a separate genus. 



