662 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 



trals (105 millimeters) is contained 12^ times in the length. The least 

 height of the tail is about equal to the length of the middle caudal rays. 

 The species is much stouter in the second half of the body than our 

 numerous examples of A. ferox. There is a well-marked fleshy keel 

 along the median line, beginning a little in front of the ventrals and 

 extending to the caudal. 



The greatest length of the bead (208 millimeters) is contained 6^ times 

 in the standard length. The width of the interorbital area (40 milli- 

 meters) is nearly equal to the diameter of the eye. The length of the 

 snout is about twice that of the eye, which is contained nearly 5 times 

 in the length of the head. The length of the intermaxillary (150 milli- 

 meters) is nearly f that of the head; the bone extends behind the eye 

 a distance equal to about ^ of the diameter of the eye. The length of 

 the mandible is about 3 times the greatest width of the head. The 

 nostril is nearly equally distant from tii> of snout and the anterior mar- 

 gin of the eye. 



The first dorsal was more or less broken, so that the lengths of its 

 rays are not fully made out. The longest ray measured 235 millimeters. 

 The distance of tbe first dorsal from the snout is about the same as the 

 length of the head. The beginning of the dorsal, tlie posterior margin 

 of the operculum, and the origin of the pectoral are in nearly the same 

 vertical. The anterior edge of the first dorsal ray is very finely ser- 

 rated. 



The distance of the adipose dorsal from the snout is 5^ times the length 

 of the head. The length of the base of this fin is f of its width at the top. 



The distance of the anal from the snout is somewhat more than 7 

 times the length of its base. The fifth, and longest, anal ray is ^ as 

 long as the intermaxillary, and 3 times as long as the last anal ray. 



The upper caudal lobe is imperfect, so that it cannot be known 

 whether or not it was prolonged into a filament. The middle rays are 

 equal to the least height of the tail. 



The outer edge of the first pectoral ray is finely serrated. The dis- 

 tance of the pectoral from the snout (223 millimeters) is 3 times the 

 length of the longest anal ray and 4 times the greatest width of the 

 head. The length of the pectoral is less than that of the head by a 

 distance equal to half the interorbital width. 



The distance of the ventral from the snout (505 millimeters) equals 4 

 times the distance from snout to nape. The length of the ventral is a 

 little more than twice that of the middle caudal rays. The first ven- 

 tral ray is perfectly smooth (serrate in A. ferox). 



Radial formula: B. 7; D. 39; A. 10; P. I, 12; V. I, 7. 



Vertebrae, 50 (as in A. ferox). 



Color. — General color dark gray, on the lower parts mingled with 

 silvery; everywhere iridescent. Dorsal membrane black with steel- 

 blue reflections. Adipose dorsal, pectorals and caudal black. Ventrals 

 and anal silvery and gray. A row of small translucent spots on each 

 side of the lateral line and keel. 



