eigenmann: the cheirodontinjE. 71 



irregular median series consisting of about eleven scales; occipital process short, 

 extending one-seventh to dorsal, bordered by three scales on each side; frontal 

 fontanel half as long as the parietal; second suborbital in contact with the pre- 

 opercle below, a broad naked area along its entire posterior margin; postorbitals 

 feeble, not covering more than half the width of the postorbital area; maxillary 

 little, if any, more than half as long as eye, slender, its margin not curved; teeth 

 small, slender, contracted at the base, with five points, the middle one being largest; 

 four teeth in the premaxillary, two in the maxillary, seven or eight graduated teeth 

 on the mandible. Gill-rakers about 7 + 10, very short, not quite one-fourth as 

 long as eye. 



Origin of dorsal a little nearer tip of snout than base of middle caudal rays or 

 the reverse. Dorsal pointed, its height equal to the length of the head, or a httle 

 longer; adipose fin well-developed; caudal lobes much longer than head; origin of 

 anal below the posterior part of the dorsal or behind the vertical from the last ray; 

 fifteen to twenty interhsemal spines, extending from near base of last anal ray to 

 caudal, with broad wings in the male; ventrals about reaching anal, pectorals a 

 little beyond origin of ventrals. Scales thin, regularly imbricate, with few radial 

 striae; caudal naked, anal with a few scales on the bases of the anterior rays. 



A large spot extending across the entire caudal peduncle, not extending on 

 the middle caudal rays. 



This species is very similar to C. piaba and C. interruptus, differing in the size 

 of the naked area of the cheek, the number of interhaemal spines, the length of the 

 maxiUary, and the number of maxillary teeth. 



38. Cheirodon interruptus (Jenyns). (Plate XII, fig. 1.) 



Tetragonopterus interruptus Jenyns, Voy. Beagle: Fishes, 1842, p. 127, tab. 23, 

 fig. 4 (Maldonado). 



Chirodon interruptus Giinther, Cat. Fishes Brit. Mus., Vol. V, 1864, p. 332; Perugia, 

 Ann. Mus. Civ. Storia Nat. Genova, (2), Vol. X, p. 45, 1891 (Rio Plata). 



Cheirodon interruptus Eigenmann & Eigenmann, Proc. U. S. Nat. Mus., Vol. XIV, 

 1891, p. 54; Ulrey, Ann. N. Y. Acad. Sci., Vol. VIII, 1895, p. 290; ? Boulenger, 

 Boll. Mus. Univ. Torino, Vol. XII, 1897 (Tala); Eigenmann, Reports Prince- 

 ton Univ. Exped. Patagonia, Vol. Ill, 1910, p. 429. 



Cheirodon monodon Cope, Proc. Am. Philos. Soc, Vol. XXXIII, 1894, p. 91 (Rio 

 Grande do Sul); Ulrey, Ann. N. Y. Acad. Sci., Vol. VIII, 1895, p. 290; Fowler, 

 Proc. Acad. Nat. Sci. Phila., 1906, p. 332 (Rio Grande do Sul); Eigenmann 

 & Ogle, Proc. U. S. Nat. Mus., Vol. XXXIII, p. 9 (Rio Grande do Sul). 



