South- American Cichlid Genus Acara. 331 



This genus is scarcely distinct from the African Para- 

 tilapia, which differs in having the maxillary more or less 

 exposed distally and in tlie constantly smaller size of the 

 scales of the thoracic region. The distinction between Acara, 

 with 3 anal spines, and Cichlosoma, with 4 or more anal 

 spines, is somewhat arbitrary, but convenient. 



Synopsis of the Species \ 



I. Praeoperculum scaleless. 



A. Dorsal and anal fins scaleless. 



1. Depth of body 2-2? in the length. 



a, 5 or 6 gill-rakers on the lower part of anterior arch. 



* 2 or 2i scales between lateral line and anterior rays of soft 

 dorsal. D. XKI-XVI 9-11. A. Ill 8-10. 



1. tetramerus. 

 ** 1 or 1| scales between lateral line and anterior rays of 

 soft dorsal, 

 t Dorsal spines subequal from about the fourth to the 

 twelfth. D. XIII-XV 10-11. A. HI ti-8. 

 J Caudal peduncle from f to as long as deep. 

 Depth of body 2-2^ in the length ; middle dorsal 



spines more than | the length of head 2. vittata. 



Depth of body 2^-21 in the length ; middle dorsal 



spines usually less than f the length of head , 3. syspilus. 



XX Caudal peduncle ^-§ as long as deep. 



4. paraguayensis. 

 tt Dorsal spines increasing in length throughout ; caudal 

 peduncle \-% as long as deep. 



D. XIII-XIV 9-11. A. Ill 7-9. Sc. 24-26 \.. 5. pulchra. 



D. (XIV) XV 10-11. A. Ill 8-9, Sc. 2G-28 -^. 6. caruhopunetata. 



b. 7 to 9 gill-raliers on the lower part of anterior arch, 



D. XlIl-XV 9-12. A. Ill 8-9. 

 Dorsal spines subequal from the fifth ; cheek with 



3 series of scales 7. cBquinoctialis, 



Dorsal spines increasing in length throughout ; 



cheek with 3 or 4 series of scales 8. riuulata. 



Dorsal spines subequal from the fourth ; cheek 



with 4 or 5 series of scales 9. Geayi. 



2. Depth of body 2i-2| in the length. 



D. Xlll-XlV 9-10. A. Ill 7-9. Caudal pe- 

 duncle longer than deep 10. zuinuretisis. 



D. XV 10. A. Ill 8. Caudal peduncle deeper 



than long 11. sapayensis. 



^ Heros centralis, Ilolmberg (Rev. Argent, i. 1891, p. 183), is an in- 

 sufficiently described species of doubtful position placed by Pellegrin in 

 this genus. It may prove to be a Geophayns of the type of G. Balzdiii, 

 Perugia. Acara niitiuta, Ilensel (xVrch. f. Nat. 1870, p. 71), appears to 

 me to be founded on young examples of Gcophayus yynmoyenys, Hensel. 



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