134 PROCEEDINGS OF THE ACADEMY OF 



fourth joint, as in other species of the group. Extremity of the abdomen 

 truncated, or slightly excavated. Color in life deep blue beneath the silvery 

 or pearly pubescence. 



Length 0*8; greatest breadth 0*29 inch. 



Its nearest ally is /. margaritacea Dana, found in the ocean between Aus- 

 tralia and New Zealand, in which the abdomen is regularly rounded at the 

 extremity, while in our species there is a well-marked angle on either side. 



On the West African genus HEMICHROMIS and descriptions of new species 

 in the Museums of the .Academy and Smithsonian Institution. 



BY THEODORE GILL. 



Mr. P. DuChaillu, the African traveller, obtained among other objects of 

 natural history, specimens of several species of fishes, one of which is a new 

 form of Peters' genus Hemichromis. 



The genus Hemichromis was proposed, in 1857, by Dr. Peters for Chromoids, 

 having the habit of Chromis or Tilapia, and with a row of conic, brown tipped 

 teeth in each jaw, the two median of which in the upper were considerably 

 larger, and also with an interior row of smaller teeth in the upper jaw. The 

 only species was obtained in Guinea by Pel. 



Recently, M. August Dumeril has described and figured a species as a new 

 generic type under the name of Chronriichthys elongatus Guichenot. It agrees 

 in every respect with Hemichromis, except in the presence of only one row of 

 teeth in the upper jaw. As, however, the inner row of Hemichromis is formed 

 by very small teeth, it is probable that it has been overlooked by Guichenot 

 and Dumeril, and that their species is therefore a genuine Hemichromis. 

 That genus will then embrace four species, which may be distinguished as 

 follows : 



Hemichromis fasciatus Peters. 



Hemichromis fasciatus Peters, Monatsberichte der Koniglichen Preuss. Akade- 

 mie die Wissenschaften zu Berlin, 1857, p. 403. 



" Fasciis transversis fuscis sex, macula operculari nigra; pinna dorsal i et 

 anali oblique fasciatis, albo marginatis ; pinna caudali supra in/raque albo margi- 

 nata; pinnis ventralibus externe fuscis." 



D. XIV. 1112. A. III. 910. 



Habitat. Guinea. (Peters.) 



Hemichromis adritus Gill. 



Fasciis quinque, latere medio expansis, macula operculari nigra, margaritacea 

 supra infra /ue m trginata ; pinnis ventralibus externe fusco-purpureis. 

 D. XIV. 11. A. III. 8. 

 Habitat. Gaboon River ? 



Hemichromis bimaculatus Gill. 



Unicolor, macula corporis latere unica et operculi apice nigris. 



1 1 3 



D. XIV. 1. Sy. A. III. 6y. Squam. ser. 25 y. 



Hemichromis elongatus Gill. 



Chromichthys elongatus (Guich.,) Dam., Archives du Museum, tome x. p. 

 257, pi. xxii. lig. 3. 

 Fasciis quinque (macula ope.rcul iri nulla) : squamis buccis quinqueseriatis. 

 D. XIII. 9. A. III. 8. 

 Habitat. Gaboon River. 



[March, 



