Fishes of the JVestern North Atlantic 



89 



Figure 2 1 . Discopyge tschudii. Left, Pelvic fins of female, 264 mm long, from off Argentina, Lat. 46°! 5' S, Long. 

 65°02' W (British Museum [Natural History]). Right, Same of male, about 400 mm long, from Argentina (U. S. 

 Nat. Mus., No. 53439). 



6 b. Posterior margins of pelvics joined across base of tail by a mem- 

 branous connection, either continuous or narrowly indented in 

 the midline (Fig. 21). Discopyge Heckel 1845.^* 



Peru, Chile, and the western 

 South Atlantic from southern 

 Argentina to Rio de la Plata. 

 5 b. Joint nasal curtain only slightly broader than long. 



Heteronarce Regan 1921.^° 

 Arabian Sea and Indian Ocean south 

 to East London, about Lat. 33° S. 

 3 b. Nostril divided into two separate apertures by a cross bridge about midway 

 of its length; teeth entirely enclosed within the mouth when latter is closed; 



39. It has long been known that females of the type species of Discopyge {Torpedo tschudii Heckel 1845) differ in a strik- 

 ing way from those of Narcine in that the pelvics are united by a membranous connection across the base of the 

 tail. This was emphasized in the original account of the species by Heckel (in Tschudi, Fauna Peruana, Ichthyol., 

 1845: 32, pi. 6) and was verified subsequently by Berg (An. Mus. nac. B.Aires, 4, 1895: 12). While the tips of 

 the pelvics of the male project a little farther rearward than in the female, they are similarly joined across the tail 

 in an Argentine specimen that we have examined (Fig. 21). The only previous illustration of the male (Stein- 

 dachner, Zool. Jb., Suppl. 4, 1898: pi. 21, fig. 14 b) shows the membrane as narrowly interrupted in the midline. 



40. Heteronarce is so close to Narcine that its generic validity is doubtful. According to its author (Regan, Ann. Mag. 

 nat. Hist., [9] 7, 192 1 : 414), it differs from Narcine only in the greater length (relative to breadth) of its nasal curtain. 

 Presumably, therefore, its type species [Heteronarce garmani Regan) has a protractile mouth with labial cartilages. 

 And Annandale's illustration (Mem. Indian Mus., 2, 1909: pi. 3 A, fig. 3) suggests that this is also the case in Nar- 

 cine mollis Lloyd (Rec. Indian Mus., I, 1907: 8), which has subsequendy been referred to Heteronarce (Fowler, 

 Bull. U.S. nat. Mus., 100 [jj], 1941: 338). 



