NO. 3 (1922) GREY MULLETS OF TUTICORIN 85 



enumeration of the points of difference in the two species therefore 

 is advisable, before the fuller description is given. 



(1) The interorbital space is slightly convex, whereas in M. 

 planiceps this area is distinctly flattened. The terms "slightly 

 convex " and "flattened " may not appear to be quite sufficiently 

 distinctive, and it must be admitted that,occasionally, the difference 

 may be a matter of opinion. At the same time, when the two species 

 are viewed together in profile, the difference is fairly obvious ; the 

 snout of M. jerdoni appears blunt, while that of M. planiceps looks 

 pointed and depressed. 



(2) The mandibular angle is distinctly obtuse when compared 

 with that of M. planiceps, which latter has been described as 



normal. 



(3) The diameter of the eye, proportionately to the length of 

 the head, is greater than in M. planiceps. 



(4) The number of scales in the lateral line are fewer in general 

 than in M. planiceps; they range from 29 to 31, most usually 30 ; 

 while in M. planiceps tney number from 31 to 34. 



(5) The lateral transverse series never exceeds 10. M. planiceps 

 may have II. 



(6) While in M. planiceps the pectoral fin has 16 rays, never 

 less, M. jerdoni has 15 equally frequently as 16. 



While most of these points in themselves are not conclusive 

 characters, used in conjunction they are sufficient to distinguish the 

 two species in question. 



The detailed description is as follows : — 



Adipose lids. — Present ; the posterior one is broad, reaching the 

 pupil, while the anterior one is narrower. 



Interorbital space.— Slightly convex. l l / 2 to 1% times the 

 diameter of the eye across. 



Uncovered chin space. — Of medium width, constricted in the 

 middle and rounded anteriorly. 



Mandibular angle. — The rami of the lower jaw meet at a pro- 

 nounced obtuse angle ; measured in degrees the angle shews a range 

 of 115 to 118. In only one case could the angle be spoken of as 

 " normal," i.e., 112°. 



Preorbital bone. — Scaled, serrated posteriorly and ventrally; its 

 strong bend approximates to a right angle. 



Maxilla. — The end of the maxilla is distinctly visible. 



