230 



Part III. — Twenty -fir si Annual Beport 



females determined. These were supplemented by similar particulars 

 obtained by Mr. P. Jamieson at the Fish-market, and the collective 

 results are here exhibited : — 



Species. 



Females. 



Males. 



Total No. 



No. 



7o 



No. 



7o 



Grey Skate {R. batis), 



666 



51 -3 



631 



48-7 



1,297 



Shagreen R&j {R. full on-ica), 



4 



50-0 



4 



50-0 



8 



Thornback Ray {R. clavata), 



660 



65-7 



344 



34-3 



1,004 



Sandy Ray {R. circularis). 



29 



61-7 



18 



38-3 



47 



Starry Ray [R. radiata), - 



510 



54-7 



422 



45-3 



932 



It will be observed that in no case do the males exceed the females in 

 number, and that with the exception of the shagreen ray, where the 

 numbers are probably too small to indicate the real proportion, the 

 females are in excess. The amount of the excess, however, varies. There 

 is almost equality in the case of the common skate, while with the thorn- 

 back, the starry ray, and the sandy ray — although here the figures are 

 small — the excess of females is very considerable. The measurements 

 are scarcely sufficiently numerous to show the relative sizes of the sexes, 

 but they suffice to indicate that the female is the larger. Thus the 

 average breadth of forty-nine female starry rays was 26-2 cm., and the 

 average breadth of thirty-one males 25*0 cm. Thirteen female thornbacks 

 had a mean width of 16'1 cm., and sixteen males a mean width of 14*2 

 cm. Six female common skates had a mean width of 41 '4 cm., and six 

 males 37'8. 



The measurements are not perhaps numerous enough to enable much 

 to be said with regard to the rate of growth except in the case of the 

 starry ray. I give some of the measurements of the latter arranged in 

 centimetre groups. 



[Table 



