8 CALIFORNIA ACADEMY OF SCIENCES 



Both pectorals and ventrals have broad, rounded outer angles, and have the 

 posterior margins straight or nearly straight when the fin is spread. The jjectoral 

 contrasts strongly with that of M. lunulatus, where the outer angle is prolonged, giv- 

 ing the fin a falcate shape. The tip of the pectoral reaches to or slightly beyond the 

 vertical from the middle of the dorsal base. The first dorsal is low, with rounded 

 anterior angle and gently concave margin, the anterior angle failing to reach the tip 

 of the posterior angle when the fin is declined. Both dorsals are longer in propor- 

 tion than they are in 31. lunulatus, and the caudal peduncle as well as the caudal fin 

 shorter. The base of the second dorsal equals in length the back of caudal peduncle; 

 the base of the anal equals in length the lower side of the caudal peduncle. The 

 bases of second dorsal and anal are much shorter than caudal peduncle in J/, lunu- 

 latus. The angle of the lower caudal lobe is rounded or slightly angulated, never 

 acute, the outline very gently concave next the angle. The margin of the posterior 

 lobe is broad, evenly truncate when spread. 



Following are measurements of a specimen from Panama: — 



mm. 



Total length 468 



Length of head (to first gill-slit) 84 



Length of head (to last gill-slit) 107 



Length of snout 41 



Diameter of orbit 10.5 



Length of spiracle 4 



Tip of snout to front of mouth 31 



Tip of snout to inner angle of nostrils 27 



Distance between nostrils 11 



Distance between angles of mouth 25 



Distance from tip of mandible to line joining posterior angles of lips 18 



Extreme length of up]5er lip 7 



Extreme length of lower lip 6 



Tip of snout to base of pectoral 107 



Width of pectoral base 24 



Outer pectoral margin 68 



Inner pectoral margin 39 



Distal pectoral margin 47 



Axil of pectorals to base of ventrals 105 



Snout to base of ventrals 233 



Outer edge of ventrals 36 



Base of ventrals 27 



Snout to base of first dorsal 152 



Base of first dorsal 52 



Height of anterior margin of first dorsal 53 



Height of posterior margin of first dorsal 17 



Distance between dorsals 100 



Base of second dorsal 41 



Back of caudal peduncle 41 



Length of upper caudal lobe 85 



Tip of caudal to base of notch 30 



Base of notch to origin of lower loijc 62 



Origin of lower lobe to base of anal 29 



Base of anal 28 



