8 CAMFOUNIA ACADKMY or SCIENCKS 



I>nlli iH'i'tonils iiiid vi'iitiiils liavr lnoiid, loiiiuli'd oiitor iiiijilcs, aiitl liavc llio 

 posterior mai-^iiis straiulil <ir nearly stiai^lit wlioii the I'm is i^proad. Tlic pccrtoral 

 contrasts stronirly witli that of M. lunulntiis, wliere the outer iii)j:;le is proloii^cd, i;iv- 

 iiij^ tlic fin II falcate shape. Tlic tip of the pectoral reaches to or slij^htly heyoiid tlic 

 vertical from the middle of the dorsal bas(>. TIk! first dorsal is low, with roiindcd 

 anterior an^le ami j:;ently concave marf^iii, the anterior angle failinj; to reach the tip 

 of the posterior an.ij;le when the fin is declined. Hoth dorsals are longer in ])ropor- 

 tion than thev are in .1/. htnnlattif^, and tiie caudal luduncle as well as the caudal tin 

 shorter. The base of the second dorsal e(|uals in length the hack of cMiidal 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 .1/. /inii>- 

 ladiK. The angle of the lower eaudal lobe is rounded or slightly angulateil, nevei' 

 nciite, the outline very gently concave next the angle. The margin of llu' po-lcrior 

 lobe is broad, evenly truncate when spread. 



Following are measurements of a specimen from Panama: — 



mm. 



Total lciii;th 4^'« 



Length of head (to first j^ill-slit) «4 



Lena^h .if head (to last gill-slit) 107 



Length of snout 4' 



Diameter of orbit 10.5 



Length of spiracle 4 



Tip of snout to front of mouth 3 ' 



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 lii)s 18 



Extreme length of upper lip 7 



E.xtreme length of lower lip 6 



Tip of snout to base of pectoral 107 



Width of [Xictoral base 24 



Outer jK-ctoral margin 68 



Inner pectoral margin 39 



Distal jiectoral 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 4 ' 



Back of caudal peduncle 41 



Length of upjier caudal lobe 85 



Tip of caudal to base of notch 3° 



Base of notch to origin of lower lobe 62 



Origin of lower lobe to base of anal 29 



Base of anal 28 



