1894.] "•*• [Cope. 



of scales above the lateral line, and has the humeral and caudal spots, 

 which are wanting in the T. pliodus. 



Hemigrammus liUETKENii Boul. Tetragonoptcrus luetkenii Boulenger, 

 Ann. Mag. Nat. Hist., 1891, p. 173. Oldrodon luetkenii von Ihring, 

 Susswass. Fische v. Bio Grande do Sul, 1893, p. 22. 



Form deep ovate, outlines of body equally convex. Profile of front 

 straight, a slight concavity above line of preopercle. Depth of body Into 

 length (less caudal fin), two and a half times ; length of head into tlie ■ 

 same, four times. Eye large, its diameter greater than length of muzzle, 

 a little less than interorbital width, and entering length of head 2.8 times. 



Scales, 32 . Radii, D. 11 ; A. 23. Pectorals not reaching ventrals, and 



ventrals not reaching anal. No teeth on the maxillary bone. Tubes of 

 lateral line on eight to twelve scales. Dorsal fin originating a little be- 

 hind vertical line of origin of ventrals. Color, silvery ; a silver band on 

 side. Humeral spot large, distinct, subround ; caudal spot distinct, ex- 

 tending to extremities of median caudal radii. 



Total length, 76 mm.; length, without caudal fin, fiO mm.; length to 

 origin of anal, 40 mm.; length to origin of ventral (oblique), 29 mm.; 

 length of head, 10 mm. 



This species differs from the H. robustulus Cope in its more compressed 

 head and in the absence of teeth on the maxillary bone. An abundant 

 species in the Jacuhy. 



Chirodon monodon sp. nov. 



A single crenate tooth on the proximal extremity of the maxillary bone. 

 General form rhombic oval. Depth in length, less caudal fin, 2.6 times ; 

 length of head in the same, 3.6 times. Ej^e large, its diameter exceeding 

 length of muzzle, equaling interorbital width, and entering length of head 



5 



3 times. Scales, 32 . Radii, D. 10 ; A. 19-22. Pectoral reaching ven- 



tral, and ventral nearly reaching anal. Origin of dorsal a little posterior 

 to that of ventral. Lateral line extending on 9-10 scales. Silvery ; an 

 indistinct, narrow, dusky line visible on the middle of the side from the 

 caudal fin to below the dorsal. 



Total length, 46 mm.; length to base of caudal fin, 35 mm.; length to 

 base of anal, 23 mm.; length to base of ventral, 15 mm.; length of head, 

 9 mm. 



This small species has a scale formula about as in the Hemigrammus 

 ihringii, but there is but one series of premaxillary teeth ; there is a 

 tooth on the base of the maxillary bone, and there are only ten dorsal 

 rays. The number of anal rays is somewhat variable. Of the three 

 specimens, one has 19 rays, the second 20, and the third 22. This is a 

 deeper bodied form than the G. pisciculus Gird., and the only other spe- 



