14 Hjalmar Ostei-gren. [No. 9 



15. Myriotrochus rinkii Steenstrup. 



Lyngen Fiord 690 37/ j^.^ 3/^ i899, 250 m., clay, + 2.8o« C. 

 Kvænangen Fiord 70» 2.5' N., -^/^ 1899, 300—343 m., clay, + 2.3« C. 

 Jokel Fiord 70» 5' N., -% 1899, 100 m., clay, + 1» C. 



These localities indicate that M, rinJcii is spread in not a little 

 degree over the colder fiords of West Finmark. I have also before 

 me a few specimens, which G. O. Saus coUected in the Varanger 

 Fiord at Vadso 70^ 3' N. The species is thus to be found even 

 in East Finmark. 



This pronounced arctic species has not been known before in 

 Norway; the statements in hterature about its occurrence on the 

 Scandinavian coast all refer to the following species (Myriotrochus 

 vitreus). This one has during the last 20 years been considered 

 identical with M. rinJcii. I have, however, found the description 

 by M. Såes U877) to be in all essential parts perfectly correct, 

 and if one compares that one with the description of M. rinlii by 

 Théel (1877), it will be found, that there are many important diffe- 

 rences. I have, by carefully comparing both species, found still 

 more differences. In order to illustrate, how distinctly these species 

 differ, I will now describe them, omitting, however, that which 

 concerns the w^hole genus Myriotrochus. 



Myriotrochus rinlii has the bodywall half transparent and 

 coloured red, just as Synapta inhærens^ to which it has, when alive, a 

 great resemblance. The red colour, hoAvever, disappears from pre- 

 served specimens. The muscles are rather strongly developed. 

 The longitudinal muscles, which are thin and broad in the hinder 

 part of the body, increase in thickness but decrease in breadth in 

 a forward dh'ection, so that they in the middle of the body are just 

 as thick as broad. In the forepart they are greatly compressed, 

 shoot deep into the cavity of the body, resembling a ribbon which 

 is fastened by one of its edges to the bodywall.') The whole dor- 

 sal surface is, except next to the lateral longitudinal muscles, 

 closely strewn with calcareous wheels, which on the middle of the 

 back, where they lie closest, number from 30 to 60 per 10 □ 

 mm. — on contracted parts they lie often partly on top of each 



1) It will be seen, that tlie longitudinal muscles closely resemble tliose of 

 several species of the genus Condrodoea. e. g. C. {Synapta) vivipara (Oested). 



