No. 3 (1922) GREY MULLETS OF TUTICORIN 77 



8. Height of fins. — The correct measuring of the height of fins 

 is often difficult in preserved specimens, since the fin becomes quite 

 rigid and may even break in an attempt to stretch it to its naturally 

 extended position ; it is frequently impossible to extend the fin fully. 

 I have therefore decided not to include relative heights of fins in 

 these descriptions. 



THE NUMBER OF FIN RAYS. 



1. The caudal Jin. — Much difficulty is experienced in the attempt 

 to count all the fin rays in the caudal fin, owing to the fact 

 that the very small rays at the edge of the fin are often indistin- 

 guishable, and only dissection could determine their exact number. 

 I have never been able to make the numbers recorded by Day tally 

 with specimens I have examined. In all counts therefore I decided 

 to include only those rays which extend to the posterior extremity 

 of the fin ; this was the method adopted by Bleeker. 1 have found 

 that in all the mullets examined 14 such rays were present. 



2. The pectoral fin. — In counting the rays of the pectoral fin, the 

 use of a lens is essential ; for large specimens a watchmaker's 

 eyeglass, and for small specimens a powerful hand lens, was used. 

 It must be remembered that there is always, in the mullets, a fin ray 

 very closely applied to the uppermost long ray ; this last closely 

 applied ray is usually quite small, and, though often easily dis- 

 tinguishable, is liable to be overlooked. 



Now, I have found that the number of rays in the pectoral 

 fin of the same species is liable to variation, and a difference of 

 as much as two has been observed ; in fact, on occasions, a differ- 

 ence of one has been noted between the two pectorals of the same 

 specimen. This fact was very disturbing for a long time, since I 

 had regarded the number of pectoral fin rays as a factor only rarely 

 liable to variation. Particular care has throughout been given to the 

 counting of these fin rays, and in the end I was obliged to regard 

 their number as of no rigid importance for mullets. 



SCALATION. 



I. The lateral line series. — The counting of the lateral line 

 series (which in the mullets, means any longitudinal series round 

 the mid-lateral area) is fairly straightforward ; the principal 

 difficulty is encountered at the base of the caudal fin, where the 



