666 PROCEEDINGS OF THE NATIONAL MUSEUM vol. us 



not Carcharodon, has a secondary lateral keel on the anterior part of 

 the caudal fin. 



Comparing the original (and some later) accounts of the nominal 

 species of Isurus with the diagnostic criteria mentioned above reveals 

 discrepancies in a few cases. For example, the original illustration of 

 Lgomphodon in Miiller and Henle (1841, pi. 28) shows the first dorsal 

 origin above the pectoral axil— a character of Lamna. However, the 

 teeth, as illustrated, are clearly those of an Isurus, and likewise there 

 is no secondary caudal keel. Miiller and Henle's illustrations are, for 

 the most part, accurate representations, so one is led to the assumption 

 that the illustration of /. gomphodon was made from a distorted 

 specimen. The type and only specimen, a mounted skin, was depos- 

 ited in the Berlin Museum but unfortunately cannot be found. 

 Compared with other makos, the illustration of /. gomphodon shows 

 a considerably shorter body sector as measured between pectoral axil 

 and pelvic origin (see table 1, E). Also the first dorsal fin is higher 

 than usual (fig. 3), and the pectoral is longer (figs. 1-2)— though not 

 as long as that of the new species described below. On this evidence 

 there is reason to believe that the skin of the type of I. gomphodon 

 underwent shrinkage along its midsector when it was being mounted. 

 Consequently, the proportions of /. gomphodon must be used with 

 caution. 



Isurus spallanzani, first illustrated in Bonaparte (1839, pi. 136, 

 fig. 1) from an Italian specunen, is also shown with the first dorsal 

 origin over the pectoral axil, but again it is clear that the specimen 

 was an Isurus. Conversely, Bonaparte's illustration (1835, pi. 134, 

 fig. 2) in the same account, of Lamna cornubica, has the first dorsal 

 origin slightly behind the pectoral posterior comer— a character of 

 Isurus. It must be presumed that Bonaparte's illustrations are 

 maccurate in these features for subsequent accounts of Isurus and 

 Lamna from Italian waters (e.g., Tortonese, 1956) do not agree with 

 Bonaparte but instead show the "normal" positioning of the first 

 dorsal fin relative to the pectoral fin. 



The above-mentioned discrepancies make understandable the con- 

 fusion which has arisen between Isurus and Lamna. The persistence 

 of such confusion is exemplified by Waite's (1921, p. 21, fig. 27) 

 illustration of an Australasian specimen of Lamna nasus as Isurus 

 glaucus. Waite's illustration was later redrawn by Barnard (1925, 

 pi. 1, fig. 6) who used it for /. glaucus in his account of South African 

 fishes. Whitley (1940, p. 123, fig. 130) also used Waite's iUustration 

 but identified the shark as /. mako. 



Isurus guentheri stands noticeably apart from the other 11 nom- 

 inal species in having many more teeth. Murray's (1884, pp. 348- 

 351) account of the type, the only information available for the species, 



