26o Memoir Sears Foundation for Marine Research 



Caudal fin: upper margin 1 8.95 lower anterior margin 8.6. 



Pectoral fin: outer margin 16.O; inner margin 11.4; distal margin 14.2. 



Distance from snout to: ist dorsal 27. i; and dorsal 61.O; upper caudal 81. i; 



pectoral 17.9; pelvics45.i; anal 66.8. 



Inters face between: ist and 2nd dorsals 2 1 . i ; 2nd dorsal and caudal 9.5 ; anal and 



caudal 6.0. 



Distance from origin to origin of: pectoral and pelvics 27.8 ; pelvics and anal 22.0. 



Since it is doubtful (see below) whether this species actually occurs in the Atlantic, 

 its most distinctive features alone need be mentioned as an aid toward its identification. It 

 falls with canis, norrisi and schmitti among the western Atlantic species in the relative 

 shortness of its head} but it is separable at a glance from norrisi by the shape of its caudal 

 (cf. Fig. 42 H with 43 D) ; from schmitti by a much smaller eye relative to the gill open- 

 ings (only about 60% as long as the 3rd gill opening in mento, but about as long as the 

 3rd gill opening in canis and schmitti), and by the shape of its caudal (cf. Fig. 42 F with 

 42 H) } from canis similarly by a small eye, by the distance between its nostrils which is 

 considerably less than V2 as great as the breadth of its mouth (approximately one-half 

 as great as that in canis) and by a relatively larger pectoral (inner margin about 1.8 times 

 as long as snout in mento and only about 1.3 times that long in canis). It differs from 

 schmitti, norrisi and canis in the fact that its teeth are symmetrical and with evenly convex 

 cutting edges. The most striking differences between mento and fasciatus are its much 

 shorter head and a caudal that has a well defined lower lobe (cf . Fig, 42 H with 43 upper) . 

 At least some of the adults of mento resemble asterias of the eastern Atlantic and Mediter- 

 ranean in being conspicuously marked with many small white spots, but mento differs 

 from asterias in the features stated in the Key, p. 242. 



Color. Adults are often conspicuously marked with many small white spots, but 

 sometimes they are plain colored,^' whereas young specimens may be marked with dark 

 colored bars. 



Range. Coasts of Peru and Chile; perhaps Argentina. 



Remarks. This species is included because a white-spotted Mustelus,'' said to be com- 

 mon in northern Argentina, seems more likely (on geographic grounds) to be mento than 

 the European asterias, under which name it was reported. 



Synonyms and References: 



Muite/us mento Cope, Proc. Amer. phil. Soc, 77, 1877: 47 (descr., Peru) Bigelow and Schroeder, Proc. 



Boston Soc. Nat. Hist., 41, 1940: 429, Table column K, pi. 14, fig. C, pi. 16, fig. D, pi. 17, fig. I, pi. 19, 



fig. C (discus.; meas.; ills, fins, teeth, denticles); Fowler, Feces Peru, Mus. Hist. Jav. Prado, 1945: 12 



(listed, Callao, Peru). 

 Mustelus edulis Perez Canto, Estud. Escual. Chile, 1886: 4 (descr., Chile); Philippi, An. Univ. Chile, 77, 



1887: 547, pi. 6, fig. 5 (descr., meas., color, ill., Chile). 



38. If our reference of edulis Perez Canto, 1886, and abbotti Evermann and Radcliffe, 1917, to the synonymy of 

 mento be correct. For discussion, see Bigelow and Schroeder (Proc. Boston Soc. nat. Hist., 41 [s], 1940: 429). 



39. Lahille, An. Mus. nac. B. Aires, 34, 1928: 310. 



