vary with age and, in fact. Smith stated in his diagnosis 

 of I. tigris that "the dorsal fin appears to become relatively- 

 higher and more acute with age." All the specimens of I. tigris 

 discussed by him are large except for one taken by Murphy (1919) 

 in New York waters. This latter specimen does not appear to 

 differ appreciably from I. oxyrinchus and is considered to be 

 this species by Bigelow and Schroeder (19W). Smith (1957) 

 suggested the possibility of three geographical subspecies of 

 I. tigris . In a still later work (Smith, I961), he recognized 

 I. glaucus and 1, oxyrinchus as before and proposed a new species, 

 I. africanus , as the third one occiirring in South African waters. 



Whitley (I929), describing a New Zealand specimen, proposed 

 a new species, I. mako, as separable (he does not say how) from I. 

 glaucus . Subsequently (Whitley, 1931)^ iie designated this form 

 as Isuropsis mako , and later (Whitley, 19^) he illustrated Isuropsis 

 mako by using a photograph of Lamna originally published by Waite 

 (1921) and improperly labelled as Isurus glaucus . Subsequent 

 accounts and illustrations of the New ZeaJ.and-Australlan form 

 suggest that it does not differ from _!. glaucus (Bigelow and Schroeder, 

 19^8). Philippi (1887) described a Lamna Huidobrii from Chilean 

 waters which, from his illustration, is clearly an Isurus , apparently 

 close to I. glaucus . 



Tamna — In the Northern Hemisphere, two species are recognized: 

 L. nasus Bonnaterre, I788 from the Atlantic, and L. ditropis Hubbs 

 and Follett, 19^7 from the Pacific, the two differing primarily in 

 snout length and coloration. In L. ditropis , the lower surface is 

 marked with black blotches, whereas it is not so marked in L. nasus. 



The relationships of these northern species with those of the 

 Southern Hemisphere have not been definitely established. Phillipps 

 (1935) described L. vhltleyi from New Zealand waters, and Whitley 

 (19^) considered the Australian form to be the same. Apparently, 

 L. whitleyi differs from L. nasus in a more posteriorly positioned 

 first dorsal fin and a longer lower caudal lobe. 



Philippi (1887) illustrated L. philippii Perez Canto, I886 

 from Chile. Although typically stout bodied, the figure shows no 

 secondary caudal keel and the teeth have no lateral denticles. 



Smith (1961) reported L. nasus from South African waters. 

 Until comprehensive comparisons can be made between species of both 

 hemispheres, the status of Southern Hemisphere forms remains uncertain. 



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