314 PROCEEiDINGS OF THE NATIONAL MUSEUM vol.94 



KEY TO THE SPECIES OF LASIANCISTRUS REPORTED FROM VENEZUELA 



la. Lower lobe of caudal fin blackish; posterior margin of caudal fin pale. 



Lasiancistrus mystacinus (Kner) 

 lb. Caudal fin barred and without a pale edge posteriorly. 



Lasiancistinis maracaiboensis, new species 



LASIANCISTRUS MYSTACINUS (Kner) 



Ancistrus mystacinus Kner, Denkschr. Akad. Wiss. Wien, vol. 7, p. 276, 1854 



(Caracas, Venezuela) (ref. copied). — Regan, Trans. Zool. Soc. London, vol. 



17, pt. 3, p. 238, 1904 (Caracas). 

 Hemiancistrus mystacinus Eigenma^;v and Eigenmann, Occ. Papers California 



Acad. Sci., vol. 1, p. 420, 1890 (Caracas). 

 Lasiancistrus mystacimis Eigenmann, Indiana Univ. Studies, vol. 7, No. 44, p. 7, 



1920 (no specimens collected). 

 Chaetostomus mystacinus GtJNTHER, Catalogue of the fishes in the British 



Museum, vol. 5, p. 244, 1864 (Caracas). 



LASIANCISTRUS MARACAIBOENSIS. new species 



Plate 11, A, B 



Because certain characters are not mentioned in the descriptions of 

 species referred to this genus, it has been difficult, if not impossible, 

 to come to definite conclusions as to the exact differences between 

 this new species and those supposed to be closely related to it. If ma- 

 terial were available for examination of each species, I would be more 

 satisfied, but the war prohibits the sending of specimens at present; 

 it is thought best, therefore, to describe this form as a new species, 

 and later, when the genus is revised, the validity of this new species 

 and of others can be determined. 



Holotype. — U.S.N.M. No. 121038, a specimen 119 mm. in standard 

 length (the largest one collected) taken by Leonard P. Schultz in the 

 Rio Socuy, 3 km. above its mouth on February 24, 1942. 



Paratypes (all collected by L. P. Schultz).— U.S.N.M. No. 121049, 

 8 specimens, 65.6 to 111 mm. in standard length, taken along with 

 the holotype and bearing the same data; U.S.N.M. No. 121043, 2 

 specimens, 37.3 and 46 mm., taken March 2, 1942, in the Rio Negro 

 below the mouth of Rio Yasa, Maracaibo Basin; U.S.N.M. No. 

 121039, 17 specimens, 23.5 to 73 mm., taken February 21, 1942, in 

 the Rio Palmar near Totuma, about 100 Ion. west of Maracaibo; 

 U.S.N.M. No. 121041, 2 specimens, 27.5 and 66.5 mm., taken March 

 6, 1942, in the Rio Palmar at the bridge 70 km. southwest of Mara- 

 caibo; U.S.N.M. No. 121046, 1 specimen, 20 mm., collected March 

 21, 1942, in a creek close by a hot spring tributary to Rio Machango, 

 about 20 km. above the bridge south of Lagunillas; U.S.N.M. No. 

 121044, 3 specimens, 33.5 to 41 mm., taken March 21, 1942, in the 

 Rio Machango 20 Ian. above the bridge south of Lagunillas; U.S.N.M. 

 No. 121048, 34 specmicns, 26.5 to 92 mm. collected March 25, 1942, 

 in the Rfo Motatan, 4 Ian. above Motatdn, Maracaibo Basin; 



