24 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. IO7 



small individuals were not used as they would distort the picture be- 

 cause of their slender bodies, short fins, large eyes, and other juvenile 

 characters. The specimens are in part in the United States National 

 Museum, Washington, D. C, and in part in the Museum of Com- 

 parative Zoology, Cambridge, Mass. The place of collection is not 

 definitely stated for some of the specimens. The data as to localities 

 are quoted from the labels as follows : Rio Grande of Brazil, S. A. ; 

 Montevideo ; off Montevideo ; Uruguay ; Uruguay River ; Paraguay - ; 

 Rio Plata and sea ; and Buenos Aires. 



Relationship. — This species, like its South American congener 

 aurea, differs from the North American species in having the scales 

 on the dorsal part of the body and at the base of the caudal fin much 

 less reduced in size. In the shape of the ventral fin they differ from 

 tyrannus and pafronus, but agree with smithi and gunteri, the outer- 

 most ray being much longer than the innermost one, giving the fin 

 an oblique margin, which is nearly straight. In tyrannus and patronus 

 on the other hand the outermost ray is not much shorter than the 

 innermost one, and the margin of the fin is definitely convex (see 

 fig. 9). The number of oblique series of scales that cross the middle 

 of the side in the South American species falls within the range of 

 tyrannus and patronus, and therefore is lower than in smithi and 

 gunteri. The South American species agree with smithi and gunteri 

 in having no small spots on the side behind the large black shoulder 

 spot, and disagree in this respect with tyrannus and patronus. The 

 differences between the two South American species recognized herein 

 are set forth in a parallel comparison in the account of aurea. 



Abundance. — B. pectinata, according to Berg (1895, p. 18), is 

 abundant during the winter in the La Plata region, and it penetrates 

 the Rio de la Plata, but seemingly not above brackish water. This 

 author, as well as Pozzi and Bordale (1935, p. 181), used the com- 

 mon name "Lacha" for this species and also for aurea, while von 

 Ihering (1940, p. 721) called them "Savelha." 



Range. — The distribution of this species, so far as known, is shown 

 by the localities given in the foregoing synonymy, and by the localities 

 listed from which specimens were examined in this study. According 

 to these the range extends from the "Rio Grande of Brazil" to Bahia 

 Blanca, Argentina. 



2 The specimens labeled "Paragua" (U.S.N.M. No. 1709), according to 

 Dr. Joao de Paiva Carvalho, S. Paulo, Brazil (personal communication), very 

 probably were taken in Paranagua Bay, situated on the northern part of the 

 coast of the state of Parana, Brazil, where Capt. Paige, aboard the U. S. S. 

 Waterwitch, seems to have collected. 



