Fishes of the Western North Atlantic 



113 



Caudal fin: upper margin 24.2; lower anterior margin 15.4. 

 Pectoral fin: outer margin 17.7; inner margin S-6\ distal margin 14.3. 

 Distance from snout to: ist dorsal 33.4; 2nd dorsal 66.3; upper caudal 76.O; pec- 

 toral 27.8 J pelvics 50.7} anal 67.0. 



Inters-pace between: ist and 2nd dorsals 24.35 ^ri'i dorsal and caudal 9.2; anal and 

 caudal 9.2. 

 Distance from origin to origin of: pectoral and pelvics 26.3 ; pelvics and anal 1 6.4. 



Trunk fusiform, much stouter than in Isurus oxyrinchus, its height opposite origin of 

 1st dorsal (where highest) about equal to distance from eye to 4th gill slit, or about 18% 

 of total length, tapering to a very slender caudal peduncle. Sides smooth, lateral line not 

 apparent. Caudal peduncle very strongly flattened dorsoventrally, widely expanded later- 

 ally and sharp-edged, with a less distinct longitudinal keel, broadly triangular in cross 

 section, on anterior part of caudal close below the rearward extension of the expanded 

 peduncle} this is more obvious in large specimens than in small j upper and lower precaudal 



Figure 15. Lamna nasus, young male, 935 mm. long, from Nahant, Massachusetts (Harv. Mus. Comp. 

 Zool., No. 209). A Second dorsal and anal fins, about 0.4 x. B Caudal peduncle viewed from above, about 

 0.4 X. C Cross section of caudal peduncle at region indicated by transverse line in B. D Caudal peduncle 

 and base of tail, from the photograph of a fresh Gulf of Maine specimen about four feet long, to show 

 secondary caudal keel. 



