1894.] 07 [Cope. 



in two series on the former and one series on the latter; no canines. 

 Nares close together. Pectoral and ventral regions compressed acute. 

 Lateral line straight, coniinuous. Ventral fins small. Gill rakers lanceo- 

 late. 



This genus is allied to Gasteropelecus, but the lateral line is of the nor- 

 mal type, that is, straight and continuous. From Piabucina, it differs in 

 having two series of premaxillary teeth, and from Chalcinus in the 

 absence of conical teeth between the dentary series. It is an interesting 

 form connecting Gasteropelecus with Chalcinus. 



Char, s'pecif. — General form rhombic, the profile straight. from the base 

 of the dorsal fin to the extremity of the muzzle. Moulh opening obliquely 

 upwards. Pectoroventral outline moderately and not extremely convex. 

 Pectoral fin elongate, falcate, reaching anal ; ventral not reaching anal. 



7 



Scales W Fin radii, D. 1.10 ; A. 37 ; V. 7 ; P. 13. Anterior rays of 



dorsal and anal fins in probably male individuals, produced, the former 

 reaching the base of the caudal. The caudal deeply emarginate. Depth 

 entering length 2.6 times ; length of head entering same four times. 

 Diameter of eye entering length of head (without chin) three times; and 

 entering the interorbital width 1.25 times. Geneial color silvery ; a 

 whiter silver band extending from near the epiclavicular region to the 

 base of the caudal fin above the lateral line. No dark markings. 



Total length, 67 mm. ; length to base of caudal fin, 52 mm ; length to 

 base of anal (oblique), 38 mm. ; length to base of dorsal (oblique), 33 mm. ; 

 length to base of ventral, 25 mm.; length to base of pectoral, 15 mm.; 

 length of head, 13.5 mm. 



This is apparently an abundant species in the Jacuhy. My specimens 

 agree with those described by Steindachner from Montevideo, except 

 that in the latter the eye is a little smaller, entering the length of the 



ead 3^ times, and there are 40-1 anal rays. The P. arc/entimtm Holmb. 

 from the Plata (Revista Argentina, 1891, p. 190) is, to judge from the 

 description, a more slender fish, with the lateral line nearer the dorsal 

 border. 



TETKA.G0NOPTERUS RUTiiiUS Jcnyns ; Steindachner, Sitzungsber. Wien 

 Akad. Wiss., November, 1876, p. 17. 



The five species of Tetragonopterus represented in the collection may 

 be distinguished synoptically as follows : 



a. No teeth on the maxillary bone. 



Scales of lateral line, 40 ; anal rays, 28 ; eyes, | head, equal interorbital 

 space ; elongate T. rntilus. 



Scales of 1.1., 36 ; anal rays, 28 ; eye, \ head, 1^ interorbital space ; or- 

 bicular T. jacuhiensis. 



Lateral line, 32-3 ; anal rays, 23 ; eye, 2.5, equal interorbital space ; 

 rhombic ^- eigenmanniorum. 



