of FijRciliid Fishes. 495 



presented by Herr J. Paul Arnold, one, Rlvulus brevis from 

 Colombia, by Dr. W. WoltcrstorfF, and the fourth, Cyno- 

 lebias melanottenia from Paranagua, by Herr A. Racliow. 



RiVULUS. 



Riculus, Poej^, Mem. Cuba, ii. 1861, p. n07. 



Cynodonichthjs, Meek, Publ. Coluiubiau Mua. Zool. v. 1904, p. 101. 



In this genus the dorsal is shorter and further back than 

 the anal. D. 6-11. A. 8-17. The pelvic tins are small. In 

 the typical species the head is depressed and the body is 

 subcylindrical anteriorly, moderately compressed posteriorly ; 

 sometimes (e. g. R. brevis) the fish is compressed through- 

 out. 



Twenty-two species from Central and South America, 

 ranging from Cuba and Southern Mexico to the La Plata. 



Synopsis of the Species. 



I. 45 to 52 scales iu a longitudinal series. 



D. 10-11. A 14-16. Dorsal origin twice as dis- 

 tant from eye as from base of caudal 1. jjeruanus. 



D. 9. A. 16-17. Dorsal origin twice or more 

 than twice as distant frorn head as from base 

 of caudal ' 2. hohnice. 



D. 8-9. A. 11-12 3. ocellatus. 



II. 36 to 42 scales in a longitudinal series. 



A. Anal ending below anterior part or middle of dorsal. 



1. D. 6-8. 



A. 11-13. Dorsal origin more than twice as disr 

 tant from head as from base of caudal, 

 Caudal with ocellus in $ , -without pale or 

 dark lower edge in c? 4. urophthalmus. 



A. 12-15. Dorsal origin about twice as distant 

 from head as from base of caudal. Caudal 

 without ocellus in 9 > with dark lower edge 

 in c? • • • ■. .- • 5. elegans. 



A. ] 1-12. Dorsal origin less than twice as dis- 

 tant from head as from base of caudal. 

 Caudal with ocellus iu 2 , with pale lower 

 edge and dark iutramarginal stripe in c? . . 6. godjuani. 



A. 11-12. Dorsal origin more than twice as dis- 

 tant from head as from base of caudal. 

 Caudal as in R. yodmq^ii 7. tenuis. 



2. D. 9-10. A. 12-14 8. fabellicauda. 



B. Anal ending below posterior part of dorsal. 



D. 10-11. A. 13 9. pylindracens. 



D. 9. A. 14. Dorsal origin 2^ head-lengths 



behind head 10. micropus. 



D. 8-10. A. 15-17. Dorsal origin less than 



2 head-lengths behind head 11. hartii. 



34* 



