668 PROCEEDINGS OF THE NATIONAL MUSEUM vol. iis 



Figure 2, where pectoral fin length as a percentage of total length 

 is expressed against total length, shows the same two groupings as in 

 figure 1. The long-finned group includes the five specimens which 

 were distinctive in figure 1 and also two more which were omitted in 

 figure 1 for lack of definite data on head length. These two are a 

 specimen from off Madagascar, reported in Fourmanoir (1961, pp. 78- 

 79), and the type of /. cepedii. Fourmanoir's records indicate that 

 he had short-finned makos as well as the long-finned specimen, and 

 he notes that there were differences in form and weight "sans pouvoir 

 definir avec certitude une deuxieme espece." One apparent error in 

 the dimensions which Fourmanoir gives for his long-finned specimen 

 (2,180 mm. total length) is the length from snout tip to pectoral 

 origin (800 mm.). This is 36.7 percent of the total length, a per- 

 centage far too great for any mako. Presumably the 800 mm. length 

 was meant to be for snout tip to first dorsal origin, as this dimension 

 is omitted for the long-finned specimen but supphed for the others. 



25- 



UJ LJ 



Z < 



a: 2 



< '"20 



§< 18 



16 



1000 1500 2000 2500 3000 



TOTAL LENGTH IN MM 



Figure 2. — Isurus, separable into long-finned and short-finned species by the length of the 

 pectoral fin relative to total length (identified specimens are types of the nominal species). 



If the type of I. cepedii rightly belongs mth the long-finned group 

 as figure 2 would indicate, then the long-finned species must take the 

 name /. cepedii. However, for the reasons given below, I do not 

 follow this course but instead describe the long-finned species as 

 new (p. 677), 



Isurus cepedii was described by Lesson (1830, p. 93) from a specimen 

 6 feet long taken in the tropical Atlantic. No illustration was 

 given, but the description, particularly of the teeth and snout, is 

 clearly that of an Isurus. The pectoral length is given as "pres 

 d'un pied et demi"; attention is drawn to the fact that this is an 

 approximate length. The color on the underside of the snout is 

 described as "Un blanc nacre," whereas in the three long-finned 



