266 



DISCOVERY REPORTS 



Disk-width frequencies of all records from the two depth categories, shown as percentages in Fig. 13, 

 clearly support the possibility of such a migration : individuals of the greater widths were more frequent 

 in the deep hauls and the smaller individuals in the shallower hauls. About the main mode, however, 

 the deep hauls show considerably greater frequencies, so that the difference is less well defined than 

 could be wished, while the adverse factor of some migrating adults being taken on the shelf is 

 unavoidable by this method of array. 



Fig. 12. Distribution of Raja brachyurops. Spring: diamonds; summer: circles; autumn: triangles- winter- squares- 

 negative observations left blank. Note. Symbols here refer to seasons, and not fo s^™" ^ 



Fig. 13 gives just a hint of possible submodes at roughly 4-5 cm. intervals that may indicate year 

 classes. Irial freehand curves drawn from grouped data by Buchanan Wollaston's (1929) method 

 show some support for this view, which seems reasonable from the annual increment of 6 cm. 

 established by Steven (1936, p. 614) for R. clavata, which is a larger species. Our data are notnumerous 

 enough for us to regard the 4-5 cm. increment for R. brachyurops as more than a possibility. 



