400 Dr. J. A. Grieg on the Age of some 



XXXIX. — Remarks on the Age of some Arctic and North' 

 Atlantic Starfishes. By James A. Grieg, Curator of the 

 Bergen Museum, Bergen, Norway. 



Dr. Mortensen lias shown, in " Smaa faunistiske og biolo- 

 giske Meddelelser " *, that ophiurids of various ages are found 

 simultaneously in shallow water at the same locality within 

 the boreal region ; transformed young were collected recently, 

 together with one-year old, Eully developed two-year old, and 

 older individuals. At Sallingsund Dr. Mortensen obtained 

 young of Ophiura ciliaris with a disc-diameter of ^-^ mm., 

 one-year old individuals with a disc -diameter of 3-4 mm., 

 two-year old ones with a disc-diameter of 7-11 mm., and 

 several whose disc-diameter was more than 12 mm. and 

 whose age was probably three years. 



The circumstances are the same on the Norwegian southern 

 and western coasts ; on the other hand. Dr. Mortensen in 

 " Echinodermsfrom East Greenland " f mentions that a large 

 number of Ophiura sarsi obtained off Jan Mayen were all of 

 about the same size (disc-diameter 15-20 mm.). As imme- 

 rous specimens o£ Ophiura robusta, a very small species, 

 were taken in the same haul, the small Ophiura sarsi could 

 not have been overlooked. At Jan Mayen there could only 

 have lived a single year-class of Ophiura sarsi, whose age 

 Dr. Mortensen estimates at one year, though I am most 

 inclined to estimate it at three years. 



An examination of the ophiurids collected by the ' Michael 

 Sars' in the Norwegian Sea shows that very often a single 

 year-class occurs at a locality, exactly as stated by Dr. Mor- 

 tensen in regard to Jan Mayen ; but several year-classes may 

 also be found — in this case, one of them is generally more 

 numerously represented than the others %. 



In this paper I shall confine my remarks to a haul which 

 the * Michael ISars ' made in the summer of 1914 off the 

 mouth of the Varanger Fjord. From this haul 157 Ophiura 

 sarsi were obtained with a disc-diauieter of 16-27 mm., and 

 one specimen measuring 11 mm. ; of tliese no fewer than 99 

 (or 63 per cent.) have a disc-diameter of 22-24 mm. — this 

 large group represents a year-class whose age must be put at 

 four years. There were also several individuals — not very 



* Vidensk. Meddel. 1897, p. 321. 



t Meddel. om Gronland, xxix. 1903, p. 82. 



X • Bergens Museums Aarbok,' 1903, no. 13, p. 23. 



