186 MEMOIRS OF THE CARNEGIE MUSEUM. 



No specimens of Sternarchella balcenops (Cope), Sternarchogiton nattereri 

 (Steindachner) and Orthosternarchus tamandua (Boulenger) were examined, and 

 no recorded regeneration for the first two species was found. However in his 

 original description of 0. tamandua, Boulenger speaks of his unique type as having 

 a regenerated caudal confluent with the anal and figures it thus (op. cit., 1898, 

 p. 427, pi. XLII). A second specimen of this same species, recorded and figured 

 by von Ihering (op. cit., 1907, p. 277, pi. VIII, fig. 1), had the same type of a regen- 

 erated caudal. 



In conclusion, eight of the fifteen species of Sternarchince are known to possess 

 the ability to regenerate muscle, fin, rays, and scales. Several of these species 

 regenerate new caudal fins from various levels more cephalad than that at which 

 the caudal fin normally occurs, entirely without, or with only a very small caudal 

 peduncle. It is probable that the other species of this group would show the same 

 type of regeneration, if enough specimens were examined, since they are so closely 

 related to the species in which these regenerations are known to occur. 



Part II. Quantitative Data. 



This section deals with several large collections of each of three species; in 

 each case all of the specimens caught at a given time and place were preserved. 

 Most of these collections were made by Dr. C. H. Eigenmann, in British Guiana 

 in 1908, and the others by the writer in the same country in 1910. The three 

 species considered are Eigenmannia virescens, Eigenmannia macrops and Sternopygus 

 macrurus. In life they all closely resemble each other, not only in color but in 

 size and shape. They are quite compressed and somewhat elongate. The body 



Fig. 29. Section showing location of air-bladder in Gymnotus carnpo Linnffius. 



tapers rather suddenly in the caudal region, which ends in a long, cylindrical caudal 

 appendage, at least one-fourth as long as the entire bod3^ The caudal appendage 

 contains a continuation of the vertebral column, enclosed in a well-scaled sheath 

 of skin. These fishes are so translucent that their blood gives them a distinctly 

 red color. The epidermis is bright yellow, and beneath it are dark blue chroma- 

 tophores, very abundant in S. macrurus, less so in E. virescens, and almost wanting 

 in E. macrops. 



In consequence of these peculiarities these species are capable of changing 

 color to some extent. In proportion to the amount of blue pigment present they 



