82 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 9 



lb. Anterior nostrils in a well-developed tube; lower jaw only slightly 

 longer than its width from rictus to rictus; pupil round, the iris 

 light except for its outer rim ; middle of the pupil directly above or 

 very slightly anterior to the middle of the lower jaw; head and 

 dorsal fin spotted or mottled (Eastern Pacific). 



2a. Eye 14 to 16.8 in head; head in trunk 7 to 8.3 ; tail 1.41 to 1.5 in 

 trunk; snout 7.4 to 8.6 in head; isthmus half again as wide as 

 diameter of eye; a pendulous, operculumlike fold of skin hanging 



down over and screening gill openings (Galapagos) 



L. opercularis, new species 



2b. Eye 12 in head; head 6.5 in trunk; tail 1.66 in trunk; snout 6 in 

 head; isthmus equal to eye; no pendulous fold of skin hanging 

 down over and covering the gill openings (Gulf of California). 

 L. pacificus Osburn and Nichols. 



Letharchus opercularis, new species 

 Plate 14 



Letharchus pacificus (nee Osburn and Nichols) Fowler, 1932, Proc. 

 U.S. Nat. Mus., vol. 80, art. 6, p. 3 (Gardner Bay, Hood Island, 

 Galapagos). — Fowler, 1938, Mon. Acad. Nat. Sci, Philadelphia, 

 no. 2, p. 251 (name only). 



Holotype. — AHF no. 15. 



Type locality. — Station 813-38, Gardner Bay, Hood Island, Galapa- 

 gos, collected at surface with electric light, January 27, 1938. 



Paratypes. — Five specimens, 190-295 mm.. Station 813-38, Gardner 

 Bay, Hood Island, Galapagos, collected at surface with electric light, 

 January 27, 1938. 



Measurements of holotype in mm. — Length 381, head and trunk 232, 

 tail 149, head 29, depth 9.6, snout 3.5, eye 1.5, cleft of mouth 4, isthmus 

 2.5. 



Description. — Body elongate, somewhat compressed, dorsally round- 

 ed, ventrally somewhat flattened. Tail much shorter than head and trunk, 

 1.57 to 1.70 in them, ending in a sharp point. Plead 12.9 to 14.1 in total 

 length, 7 to 8.3 in trunk, 8 to 9.3 in head and trunk. Depth 29.1 to 39.6 

 in total length, 2.3 to 3.02 in head. Snout 7.4 to 8.6 in head; eye 14 to 

 16.8 in head, 2 to 2.3 in snout. Isthmus much wider than diameter of eye. 

 Skin smooth and naked. Mouth inferior; lower jaw much shorter than 



