28 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 119 



scribed the fish from IS specimens collected by Frederick C. Hartt 

 somewhere along the "Lower Amazon." Hiibbs (1926), after ex- 

 aminmg the specmiens, reported that the fish belongs to the genus 

 Naiuiostomus and at that time Eigenmann, in personal communication 

 with Hubbs, concurred in this referral. Neither Hubbs, Eigenmann, 

 nor anyone else has tried to identify Eigenmann's syntypes of amazona 

 with any known species of Nannostomus. Unfortunately, a check of 

 various American museums and with Dr. Hubbs has not located the 

 type specimens. From examination of Eigenmann's original de- 

 scription it seems probable that two species, Nannostomus marginatus 

 and N. trifasciatus, were among the original specimens. Measure- 

 ments and counts include the range of both species, and the color 

 description could be of either species. It seems likely that the male 

 mentioned by Eigenmann is N. marginatus but that some of the other 

 spechuens are most probably N. trifasciatus. The name trifasciatus 

 Steindachner 1S76 predates amazona Eigenmann 1S94; however, 

 amazona predates jnarginatus Eigenmann 1909; N'annostomiis mar- 

 ginatus is a well-established name, especially in the aquarium litera- 

 ture, where it is used frequently. It would serve no useful purpose 

 to substitute the name amazonus for marginatus, especially since 

 some of the syntypes at least appear to have been trifasciatus. If 

 the types of amazona are ever found and some of them prove to be 

 trifasciatus, one of these should be selected as the lectotype and 

 Cyprinodon amazona placed in the synonymy of Nannostomus 

 trifasciatus. 



Diagnosis. — This species, like Nannostomus heckjordi, lacks obvious 

 unique characters, but it may be readily diagnosed by the following 

 combination of characters: Anal fin rays completely unmodified; gill 

 rakers 9 + 13; scales in a lateral series 26-27; perforated lateral-line 

 scales 3 to 5; one maxillary tooth present; primary, secondary, and 

 tertiary horizontal stripes present; 11 teeth in second tooth row of 

 dentar}'. 



Descriptiox. — Body elongate, somewhat cylindi-ical through an- 

 terior half, but sides flattened and body compressed posteriorly. 

 Greatest depth lying between posterior tip of appressed pectorals 

 and origin of dorsal fin. Standard length of largest specimen 28. 2 

 mm. (a larger aquarium specimen, a male, measured at 32.5 mm.). 

 Greatest body depth 4.6 (4.5-4.7) ; least depth of caudal peduncle 

 10.2 (10.0-10.4); length of caudal peduncle (including both sexes) 

 5.8 (5.6-6.1); snout tip to origm of dorsal 1.9 (1.8-2.0); snout tip to 

 origin of anal 1.28 (1.27-1.30). 



Head elongate, rather depressed, especially in snout region; top of 

 head only slightly convex between ej^es. Snout obtuse, especially 

 so in dorsal profile. Head 3.6 (3.4-3.9) [Peruvian specimens 3.7-3.9, 



