18 Hjalmar Ostergren. [No. 9 



this is possibly due to some external injury or local maceration, in- 

 flicted by the preservation. It may also be possible, that an abrasion 

 of the skin covering single wheels takes place also in living speci- 

 mens, which otherwise are quite uninjured. 



When Danielssen and Koeen (1882) say, that the wheels in 

 M. rinkii are stalked, they seem in reality to mean that they lie 

 in warts, which rise above the level of the rest of the skin, because 

 they say, like Théel, that they lie „in the layer of connective 

 tissue underneath the epithelium". As also Théel (1886) supposes, 

 the wheels in the living animal can, together with surrounding tissues, 

 depending upon different degrees of contraction, protrude to various 

 heights beyond the level surface of the skin. 



16. Myriotrochus vitreus (M. Såes). 



Syn. Oligotrochus vitreus M. Såes. 



Brettesnes 680 12' N., 16/2 1899, 350-400 m., clay, -f- «.S» C. 



This species is even by G. 0. Såes found in the same district 

 (Skraaven 68° 10' N.) at a depth of up to 550 m. (M. Saes 1877). 

 Besides, it is to be met with along the whole of the Norwegian 

 coast even down to Skager Rack, but is not known in any other 

 district. It lives at a depth of 100 — 700 m. and, as far as is known, 

 only where the temperature all the year round keeps at + 5° to 

 -f 8° C. 



In this species the bodywall is thin, perfectly transparent, 

 nearly as clear as glass, so that the intestines can clearly be seen. 

 Sometimes, according to Saes, it may have a weak tinge of 

 colour — a greenish or at the ends of the body reddish tint; as 

 a rule it is perfectly colourless. In preserved specimens the trans- 

 parency is less, still always far greater than in the preceding species. 

 The muscles are very weak ; the longitudinal muscles increase some- 

 what in thickness in the forepart of the body, but are first equal 

 in thickness and breadth just behind the calcareous ring. They are 

 very thin in all the rest of the body. The calcareous deposits are 

 completely wanting in the middle and biggest part of the bodywall, 

 on the dorsal surface as well as on the ventral surface. At both 

 ends of the body one finds, as a rule, some few thinly scattered 

 wheels, principally on the back. The greatest number of wheels I 



