No. 3 (1922) GREY MULLETS OF TUTICORIN 75 



only rarely need one be in doubt as to whether a specimen may 

 safely be regarded as possessing adipose eyelids. This division 

 into sub-genera has been adopted here, and for the eight species 

 described, four belong to Mugil and four to Liza. 



The species recognized from Tuticorin waters are: — 



(1) Mugil cep/ialottis Cuv. & Val. (Mugil oeur Forsk.). 



(2) Mugil planiceps Cuv. & Val. 



(3) Mugil jcrdoni Day. 



(4) Mugil kelaartii Giinther. 



(5) Liza troschelii (Bleeker). 



(6) Liza amarula (Cuv. & Val.). 



(7) Liza caeruleo-maculata (Lacepede). 



(8) Liza waigiensis (Quoy & Gaimard). 



THE CRITERIA. 



MEASUREMENTS. 



I. Length of body- The practice generally adopted in the past 

 for measuring the length of the body of fishes has been to include 

 the caudal fin in the measurement ; but it has recently been pointed 

 out that since the caudal fin is only comparable to other median 

 fins, it should not be included, any more than a dorsal or anal fin is 

 included in the measurement of the depth of the body. While 

 recognizing the force of this argument and sympathizing with it, 

 I have, nevertheless, included the caudal fin in the measurement of 

 the total length, and therefore in the proportions, given here. And 

 for the following reasons : there is absolutely no difficulty in deter- 

 mining the length when an overall measurement is taken ; it is 

 arbitrary and quite definite, allowing of no individual opinions as 

 to limits. If, however, the caudal fin be omitted, there at once arises 

 the necessity of deciding the exact line passing vertically through 

 the base of the fin ; different workers may fix different points, 

 particularly when, as in the case of mullets, there is no sharp finish 

 to the base of the caudal fin. 



A practical point is also involved: when large numbers of 

 fishes are to be measured, the time taken becomes an important 

 factor, and the figure can be much more readily determined when 

 an overall measurement is taken ; much hesitation results from 

 attempting to measure to the base of the caudal, for to be exact, the 

 fish must be removed slightly from the measuring scale, and a line 

 continued through the base of the fin to the scale. 



