eigenmann: the FRESHWATER FISHES OF BRITISH GUIANA 145 



I have also examined the specimens in the Leiden Museum. 



This species differs from Notarius parmocassis in having the occipital process 

 still narrower, the margins being little convex. No teeth on vomer; no patches 

 behind the two triangular palatine patches. 



L 



Fig. 30. Outlines of occipital processes of three specimens of Notarius stricticassis (Cuvier and 

 Valenciennes). Total length of specimens the processes of which are figured in order from left to right: 

 280 mm.; 400 mm.; 405 mm. 



Arius Cuvier and Valenciennes. 

 Arius Cuvier and Valenciennes, Hist. Nat. Poiss., XV, 1840, 53. — Bleeker, 



Ichth. Arch. Ind. Prodr., I, 1858, 62, 67 (arius). 



Type, Pimelodus arius Buchanan. 



Palatine patches of teeth without a backward projecting angle; teeth of the 

 palate granular, none on the vomer; gill-membranes united to the isthmus, with a 

 very narrow free margin across the latter. 



23. Arius spixi (Agassiz). 11 (Plate IX, fig. 2.) 



Pimelodus abidus Spix, Selecta Gen. et Spec. Pise. Bras., 1829, pi. 7, fig. 1 (Equa- 

 torial Brazil). 



Pimelodus spixii Agassiz, Selecta Gen. et Spec. Pise. Bras., 1829, 19. 



Arius spixii Cuvier and Valenciennes, Hist. Nat. Poiss., XV, 1840, 76 (copied). 



Tachisurus spixii Eigenmann and Eigenmann, Proc. Cal. Acad. Sci., (2), 1, 1888, 

 146 (Maranhao; Bahia; Rio Janeiro; Para,; Santos in Sao Paulo; Abrolhos); 

 Occasional Papers Cal. Acad. Sci., I, 1890, 88. — Jordan and Evermann, Bull. 

 U. S. Nat. Mus. No. 47, I, 1896, 131. 



Arius arenatus Cuvier and Valenciennes, Hist. Nat. Poiss., XV, 1840, 106 (Cay- 

 enne). — Gunther, Catalogue, V, 1864, 172 (copied). — Bleeker, " Silures de 

 Suriname," 1864, 53, pi. 4, fig. 2 (Surinam). 



Galeichthys arenatus Jordan, Proc. U. S. Nat. Mus., IX, 1886, 558 (name only). 



Arius nuchalis Gunther, Catalogue, V, 1864, 171 (British Guiana). 



Galeichthys nuchalis Jordan, Proc. U. S. Nat. Mus., IX, 1886, 559 (name only). 



11 Two specimens of fissus from Cayenne (from the Paris Museum) and one from Surinam (all in 

 the museum at Leiden) have head 3.4 and 3.6 in the length; otherwise they are very similar to the specimens 

 of arenatus ( = spixi) with head 3.9 in the length. The palatine patches of teeth are also smaller. 



