EDWIN CHAPIN STARKS 17 



49. Chalcinus rotundus (Schomburgk). 



One specimen was taken by Dr. Baker and Mr. Mann at the mouth of 

 the Rio Madeira. Comparing it with a specimen collected by Dr. Eigen- 

 mann at British Guiana it differs only in having no dark pigment anywhere 

 on the fins or body. 



50. Chalcinus elongatus Gunther. 



A number of small specimens up to 8 inches in length were taken at 

 Para. The length of the pectoral is usually equal to half of the distance 

 between the snout and the dorsal, but it varies from this to half of the 

 distance between the snout and the last dorsal ray. It reaches to the middle 

 of the ventral, which reaches half way from its base to the anal. The front 

 of the anal is under the last dorsal ray or a little behind. The pectorals 

 are sometimes colorless or sometimes dark with fine black points. The 

 adipose dorsal is over the last anal ray and coterminous with it, or often 

 the latter projects a trifle farther back. 



51. Piabucus dentatus Koelreuter. 



Three specimens, the largest 6 inches in length, were obtained at Para. 

 They agree very well with the description published by Dr. Eigenmann 

 (F. W. Fish, of Brit. Guiana, p. 316) except in depth of body. It is there 

 stated to be 3.6 of the length. Giinther (Cat. V., p. 343) gives the depth 

 as one-fifth or one-sixth of the total length, including the caudal, and the 

 picture published by Bloch (Ausl. Fische, p. 382) agrees with this. In my 

 specimens the depth is from Ay^ to 4^ in the length to the caudal base, 

 or 5^4 to 5^ with the caudal. It is possible that Dr. Eigenmann's descrip- 

 tion should read 4.6 rather than 3.6. 



52. Pygoprlstis gibbosus Starks, new species. 



Plate 3. 



Though this species was found to be one of the most common of the 

 forms related to Serrasalmo in the market at Para it seems to have remained 

 undescribed, for it has been referred to Pygoprlstis dcnticulatus. 



The type of Pygoprlstis denticulatus came from British Guiana, and 

 as the specimen with which I compare this species was collected by Dr. 

 Eigenmann at Lama Stop-off, British Guiana, there is every reason to sup- 

 pose that it is a representative of that species. 



The depth in front of the dorsal is contained in the length 1^ times, 

 or sometimes a trifle less. In P. denticulatus it is 1^ times (though Dr. 

 Eigenmann reports 1.66). The outline of the body is much more angu- 



