404 Dr. J. A. Grieg on the Age of some 
this locality a maximum at 8-10 mm., while at the station 
off the coast of Romsdal it was at 7-9 mm. The difference 
must be attributed to the fact that there were better conditions 
of life at the one locality than at the other. 
Quite the same result that the Fro Islands material gives 
is exhibited by 55 specimens from a locality in the Kara Sea. 
As the table shows there is a marked maximum of 49 speci- 
mens at 3-5 mm., while only 5 specimens have a disc-radius 
of 7-10 mm. From another locality in the Kara Sea there 
are 37 specimens, which show that three year-classes may be 
represented at a locality, but only one of them numerously. 
We have first a large group of 29 specimens which have a 
disc-radius of 2-7 mm., with a maximum of 22 specimens at 
38-5 mm. ‘Then, a group of 7 specimens with a disc-radius 
of 9-13 mm., and, finally, one specimen of 23 mm. Hach of 
these groups must represent an annual class, the youngest of 
which only was numerous. 
The material of Pontaster tenuispinus examined by me 
shows that this species has a year-class at 3-4 mm., another 
at 8-10 mm., and I have had some specimens with a disc- 
radius of more than 13 mm. The material of this last group 
is unfortunately so sparing that it has not been possible to 
determine where its maximum is to be found; I should be 
inclined to think that it must be looked for at about a radius 
of 156 mm. With a disc-radius of 23 mm. Pontaster tenui- 
spinus has attained its maximum of growth. Whether it is 
possible to find one or two year-classes between 13 mm. and 
23 mm. cannot at present be definitely determined, but I am 
most inclined to think that representatives of two year-classes 
are to be found between these two sizes. 
From three localities in the Barent’s Sea I have measured 
169, 149, and 335 specimens respectively of Ctenodiscus 
crispatus. The specimens from the first locality measured 
3-13 mm. and had a maximum of 128 specimens (or 77°7 per 
cent. of the total number) at 7-10 mm. ; at the second locality 
there was a maximum of 132 specimens (or 88°6 per cent.) at 
8-11 mm.—these specimens measured 6-13 mm. ; at the third 
locality the specimens measured 6-16 mm.—at 9-12 mm. 
there was a maximum of 267 specimens (or 79°7 per cent. of 
the total number). If we compare the material, we find that 
the majority of the specimens at all three localities are of the 
same size and represent the same annual class. It is very 
probable, however, that at two of the localities, at least, there 
were specimens of still another year-class, for material from 
other localities indicates that the smallest specimens from the 
