Natural History of East Finmark. 416 



I dredged Mi/riotrochus Rlnk'd in 1890 in 2-5 fathoms in 

 Klosterelv Fiord, and in 5-30 fathoms in the inner part of 

 Lang Fiord. 



The two forms above referred to are the only known 

 recent representatives of the genus ; but M. Sehlumberger 

 has described under the name Stiisria elegans ('^Notesur 

 les Holothuridees du Calcairc Grossier," Bull. Soc. Gcol. dc 

 France, ser. 3, vol. xvi. p. 440, figs. 12-14) spicules which it 

 seems difficult to distinguish from those of the recent form. 

 In a subsequent paper {" SecondeNote sur les Holothuridees 

 fossiles du Calcaire Grossier/^ /. c. vol. xviii. p. 191) 

 M. Sehlumberger refers the species which he had previously 

 described to the genus Myriotrochus, and adds a second 

 fossil species, Myriotrochus operculum. 



The wheel-spicules of Myriotrochus Rlnkii are very 

 beautiful objects. Most of the illustrations 'which have 

 been already given are not fully satisfactory, as not giving 

 a side view ; but the oblique figures of Ludvig (figs. 12 & 13) 

 are excellent. His fig. 14 seems to have been drawn from a 

 specimen in which calcification has been carried further than 

 in any specimen previously figured or in any that I have 

 myself seen. The spokes have widened at the middle of their 

 length and become united with each other, but small inter- 

 vening spaces remain open near their junction with the 

 central boss. 



In the early stage of a wheel from the central boss there 

 are developed all round radiating bars or spokes (fig. 5), 

 These spokes at their distal extremity then widen out late- 

 rally, and, uniting with each other, form the tyre which 

 completes the wheel ; then from the uj)per and inner edge 

 of the tyre a series of triangular processes are projected hori- 

 zontally inwards, and overhang the spokes which are attached 

 to the other edge of the tyre ; these triangular lobes are 

 always somewhat more numerous than the spokes. The 

 structure will be best understood by comparison of the figures 

 here given — fig. 6 representing the upper, fig. 7 the under 

 surface, and fig. 8 the wheel as seen obliquely. The spokes 

 at their attachment to the central boss are bent slightly 

 upwards, and then with a gentle arching curve downwards and 

 ultimately upwards again they form junction with the tyre'^. 

 The double bend of the spokes, which is very elegant in itself, 

 keeps the entire thickness of the wheel as seen from the side 

 (fig. 9). I do not find any material difi:crence in the wheels 

 of this species as found in East Finmark when compared 



* Ludvig .s fig. 13 admirably illustrates tbe double curve of the spokes-. 



