1890.] 



SEXUAL CHARACTERS OF ARNOGLOSSUS. 



541 



tliat this was true in every case without exception, and having traced 

 the gradual development of the peculiar character in the males, I 

 no longer had any doubt that the two forms belong to a single 

 sexually dimorphic species. I will now describe the differences 

 between the two forms in some detail. 



The largest specimens of the male, or lophotes form, are 20 cm. 

 long including the tail. The first dorsal ray is not elongated, and 

 its length is contained 4| times in the length of the head ; it is thin 

 and flexible and arises from the right side of the head, not from the 

 edge. The 2nd, 3rd, 4th, 5th, and 6th dorsal fin -rays are elongated, 

 the order of magnitude being 4th, 3rd, 5th, 2nd, 6th ; the fourth ray 

 in a specimen of the length just mentioned measured 3*2 cm. or five 

 sixths of tbe length of the head. 



The rays of the left pelvic fin, excepting the first, are also elon- 

 gated as compared with those of the female, the 4th being the longest. 

 In the specimen mentioned it was 2 cm. long, or half the length of 

 the head. 



The eyes in the male are slightly larger than those of the female, 

 as the following measurements show (the total length given in- 

 cludes the tail; the eyes were measured along the longitudinal 

 diameter): — 



Total length. Diameter of eye. 



fl3"2cm. 6-5 mm. 



17"4cm. 8-75 mm. 



18-4 cm. 10-0 



Females 



f 13-7 cm. 

 I 17-6 cm. 

 i 18-7 cm. 



mm. 



7*0 mm, 

 8*5 mm. 

 9-25 mm. 



The length of the upper jaw measured from its anterior extremity 

 to the posterior end of the maxilla on the upper side is slightly 

 smaller in the male than in the female, as the following measure- 

 ments show : — 



ToUl length. Length of upper jaw. 



J 19-1 cm. 11-25 mm. 



• [ 18-4 cm. 



Males 



Females . 



ri8-7 

 • 118-5 



cm. 

 b cm. 



10*5 mm. 



12-0 mm. 

 11-25 mm. 



Up to the length of 13-2 cm. the males do not show any elongation 

 of the rays of the dorsal or pelvic fins, and therefore do not differ in 

 this respect from the females. But in male specimens 14-7 cm. 

 long the character is already well-marked, tbe longest dorsal ray 

 in a specimen of this length being five sixths of the length of the 

 head, as in a full-grown specimen. 



In the full-grown adult female the character so conspicuous in 

 the male is slightly but distinctly developed, that is to say some of 

 the anterior dorsal fin-rays are slightly elongated. The 2nd, 3rd, 



