of the Fishery Board for Scotland. 



127 



In the second anal luscus and minutus are again in close agreement 

 with averages of 21 and 22 respectively, while esmarkii shows an average 

 of 27 rays. 



EsmarTcii has a much larger number of fin-rays than either luscus 

 or minutus. 



The average number of fin-rays in all three dorsals is, for luscus 56; 

 minutus, 57; and esmarMi, 66. 



It was [noticed above that the extent of the dorsal edge which bore 

 fin-rays was the same in all three species. It therefore follows that in 

 esmarkii we have to deal with a rather lighter and less robust ray than in 

 the two others. 



The anal rays (first and second) amount to 55 in the case of luscus, 50 

 in minutus, and 56 in esmarkii. Here luscus has a total of 55 rays 

 distributed on a portion of the ventral edge equal to 50 per cent, of the 

 length of the fish, while minutus has 50 rays on 46 per cent, of the 

 length, and esmarkii has 56 rays on a part equal to 45 per cent, of the 

 length of the fish. In the anal fin-bearing part we have in esmarkii a 

 greater number of rays to the unit of length than in luscus and minutus. 



If, now, we divide the average length of the fin-base by the average 

 number of rays we shall get a relative index of the robustness of the fin- 

 rays in the different species, and in the different fins of the same species. 



Average Index of Fin-rays for each Fin. 



Species. 



1 D. 



2d. 



3d. 



1 A. 



2 a. 



G. luscus, 



•8 



1-07 



•65 



1-17 



•71 



G. minutus, 



•84 



104 



•71 



1-1 



•7 



G. esmarkii, 



•8 



•88 



•63 



•96 



•63 



The index of the fin-ray of esmarkii is smaller than those of luscus 

 and minutus, in all the fins except the first. There is also to be noticed 

 that in each species the indices of the third dorsal and second anal agree 

 closely, and together differ from the indices of the second dorsal and first 

 anal fins. In the two former fins the rays are set more closely together, 

 which probably means that they are less robust rays than those of the 

 other fins. 



The three species agree fairly closely in their respective indices for the 

 first dorsal fin. In all three species the indices for this fin are less than 

 those of the second dorsal and first anal fins. 



From the Tables given above it is seen that there is no typical generic 

 number of rays either for the dorsal or anal group. In the two closely 

 related forms, luscus and minutus, there is an almost identical number of 

 fin-rays for each fin in the dorsal group, but they are both widely 

 separated from esmarkii in this comparison. In the matter of the anal 

 fin-rays, luscus aud minutus were separated. Here the anal rays have a 

 specific value. The dorsal fins are together, on the other hand, a sub- 

 generic character. The extent of the dorsal edge of the body furnished 

 with fin-rays is the same in all three species ; but the quality of the rays 

 is specific, and involves different numbers. 



