90 



PROCEEDINGS OF THE NA TIONAL MUSEUM. 



VOL. XXXI. 



The plates counted in the series in the middle line of body are uni- 

 formly 28, in the series just below the dorsal, 30; the dorsal formula 

 is always I, 7, and the anal rays 5. There are minute spines on the 

 edge of the ope role; dorsal base considerably shorter than the distance 

 from posterior dorsal ray to adipose, pectoral reaching somewhat 

 beyond base of ventral and the ventral a little beyond anal. 



The accompanying table shows some unimportant variation in pro- 

 portional measurements according to the size of the individual: 



Proportional measurements of Plecostomus cordovx. 



a Head measured from tip of snout to end of occiput. 



b Head measured from tip of snout to upper end of gill-opening. 



Family GYMNOTID.E. 



30. EIGENMANNIA VIRESCENS (Valenciennes). 

 PEZ-ESPADA OR MACHETA. 



Sternarchus virescens, Valenciennes in D'Orbi^ny, Voy. Amer. Merid., 1847, Pt. 



2, V, p. 11, pi. XIII, fig. 2. — Weyenbergh, Act. Acad. Nac. Cien. Cordova, 



111, 1877, p. 6 (Las Agnas de Santa Fe). 

 Eigenmannia virescens, Eigenmann and Kennedy, Proc. Ac. Nat. Sci. Phila. 1903, 



p. 530 (Matto Grosso or Asuncion, Arroyo Trementina). — Eigenmann and 



Ward, Proc. Wash. Ac. Sci., VII, 1905, p. 5 (Rio Magdalena to Rio de la 



Plata, east of the Andes). 



We have one specimen w hich we identify as this species, although 

 it disagrees slightly with the descriptions. It is a female 13.75 inches 

 long, full of ripe eggs. 



Head in total length about l^.Ott; depth 8.8; tail from posterior 

 base of anal about 3.92 in total length; eye 4.25 in head; snout 28.8; 

 pectoral about 1.13 in head; anal rays 232; scales on lateral line to 

 opposite posterior base of anal 123. 



Family PCECILIID.E. 



31. CNESTERODON DECEMMACULATUS (Jenyns). 



Pcecilia decem-manilatns Jenyns, Zool. Voy. Beagle, Pt. 4, Fish, 1842, p. 115, 



Maldonado. 

 Girardinus deceminaculatus, Perugia, Ann. Mus. Civ. Stor. Nat. Geuova, 2d ser., 



X (XXX), 1890-91, p. 253 (La Plata). 



