166 MEMOIRS OF THE CARNEGIE MUSEUM. 



III. Steatogenys elegans (Steindachner). 



In the original description of this species Steindachner'" notes a pair of cylin- 

 drical filaments which lie in grooves on each side of the mental region and a second 

 pair of skinny flaps, one of which projects from a groove on each side above the 

 pectorals. Boulenger^' placed this species in a separate genus because of these 

 peculiar filaments. Neither of these pairs of filaments has been studied farther, 

 since very few specimens of this species have been collected. 



Specimens of this species in the collections made by Dr. Eigenmann and by 

 Mr. Haseman make a detailed study of these filaments possible, and subsequently 

 I obtained six specimens while in British Guiana. Only a short account of these 

 organs is given here, as they are to be more fully described in a separate paper. 



The mental filaments begin near the lower margin of the pectorals, curving 

 downward and inward until the rhiddle of the mental region is reached. They 

 terminate side by side about two millimeters from the edge of the lower pair. 

 Each filament is covered for its entire length, except at its termination, by a thin 

 transparent membrane. About a millimeter from the tip of each filament this 

 membrane separates, leaving a median, oval area exposed. In preserved specimens 

 this membrane may easily be torn and the entire filament lifted out of the containing 

 groove to its attachment below the pectoral. The filaments are about twelve 

 millimeters long and half a millimeter in diameter. In life they are transparent, 

 but when preserved they become fatty in appearance and show numerous opaque 

 cross-bands. These bands are plate-like structures, which cross the cylindrical 

 filaments at about right angles, and on both surfaces bear small papillae. The 

 plates in the specimens so far examined vary in number from sixty-eight to eighty 

 in each filament. On the proximal (i. e., dorsal) edge of each filament a large nerve 

 runs the entire length of the filament and distributes its fibers to the plates. The 

 space between the plates is crossed about midway by a very delicate partition. 

 The lateral filaments, called skinny flaps by Steindachner, are much like the 

 mental filaments. Each lies in a groove, which begins just above and behind the 

 origin of the pectorals and curves upward and backward from its base, a thinner 

 portion extends downward behind the pectorals to the origin of the ventral filament. 

 The histological structure of these filaments shows many points of similarity with 

 that of the electric tissue of the electric eel. For the present, at least, these struc- 

 tures are considered as electric, or pseudo-electric, organs. 



IV. Othei- Pseudo-electric Organs. 



A paired organ made up of long fibers was found in Sternarchus albifrons 

 (Linnaeus) and Sternarchus hasemani sp. nov., running from just behind the viscera 

 to about the middle of the caudal region. The two halves of this organ lie in the 



'" Steindachner, Fish-Fauna Cauca-Guayaquil, 1880, p. 37. 

 " Boulenger, Trans. Zool. Soc, Lond., XIV, 1898, p. 428. 



* A Study of the Submental Organs of Slealogenys elegans, etc., by Annie Lowrey. In press. Miss 

 Lowrey finds the submental organs to agree histologically with the electric tissues of E. ekctricus. 



