482 BULLETIN 189, UNITED STATES NATIONAL MUSEUM 



de Afuera by R. E. Coker. These two specimens apparently are the 

 only ones known from Peru, and form the basis for the foregoing 

 description. The shape of the second dorsal, caudal, and anal fins 

 change greatly with age, as indicated in the description, and as shown 

 by other specimens from Panama Bay. It is evident, also, from the 

 Panama material that these fins are not always miiformly developed 

 in specimens of equal size. 



Although the Peruvian examples herein have been identified with 

 northern material (chiefly from Panama Bay), differences in the num- 

 ber of fin rays of the limited material now at hand indicate that they 

 probably are subspecifically distinct. The second dorsal has 26 rays 

 in each of the Peruvian examples, whereas in 19 specimens from Pan- 



FiGURE 91. — Balistes polylepis Steindachner. From a specimen 450 mm. long with a 

 slightly abnormal caudal fin, Lobos de Afuera Island, Peru (U.S.N.M. No. 77679). (After 

 Evermann and Radcliffe, 1917.) 



ama Bay 3 have 26 rays, 12 have 27, and 4 have 28. The anal has 



23 rays in 1 of the Peruvian specimens and 24 in the other, while in 

 the 19 specimens from Panama Bay it has 23 rays in 1 specimen, 



24 rays in 2 examples, 25 in 14, and 26 in 2. The pectoral has 13 

 rays in each Peruvian example, compared with 13 rays in 2 examples, 

 14 in 16, and 15 in 1 specimen from Panama Bay. 



Range. — Baja California to northern Peru. 



Genus CANTHIDERMIS Swainson, 1839 



Body somewhat elongate, compressed; snout long, rather blunt; 

 teeth strong, generally notched; gill opening an oblique slit, surrounded 

 by ordinary scales (with no enlarged bony scutes behind it as in 



