EIGENMANN: THE FRESHWATER FISHES OF BRITISH GUIANA 141 



Distance of dorsal spine from snout 2.5-2.75 in the length; dorsal and pectoral 

 spines subterete, the outer margin roughened, the sides striate; the dorsal spine 

 slightly serrate behind, a little shorter than the pectoral spine, 1.4-1.6 in the head; 

 pectoral spine strongly serrate behind. Space between the dorsal and adipose fins 

 3.6-4 in the length. Adipose fin as long as the dorsal. Upper caudal lobe the 

 longer, about 4 in the length. Anal as high as long, 2 in head. Ventral 1.6-2 in 

 head. Pectoral pore minute; sides with vertical series of pores. Plumbeous above, 

 silvery on sides, fins dusky. 



I have examined the types of coelestinus, hymenorhinus, dubius, and mesops. 

 They are all identical with herzbergi. 



In the types of Bagrus coelestinus Miiller and Troschel in the Berlin Museum, 

 215-275 mm. long, from Guiana, there is a distinct but narrow streak between the 

 posterior nostrils. The teeth are just as in a specimen of herzbergi 270 mm., col- 

 lected by me. 



The mesops of Miiller and Troschel, about 320 mm., is like coelestinus, but 

 the posterior patches of teeth are not so highly developed as in the latter. 



Fig. 26. Teeth of Selenaspis herzbergi (Bloch). Total length of specimens the teeth of which are fig- 

 ured in order from left to right: 140 mm.; 240 mm.; 300 mm. , 



Three specimens of herzbergi, hymenorhinus, and dubius, 255, 207, and 170 mm. 

 long, in the Leiden Museum, have the dorsal aspect of the head alike, and the maxil- 

 lary barbels extend respectively not quite to the end of the pectoral, to the ventral, 

 and a little beyond the origin of the ventral. The internasal membrane is most devel- 

 oped in the largest and least in the smallest specimen. In the second in size the 

 posterior palatine patches are not developed, corresponding with a specimen 210 

 mm. long collected by me and now in the Berlin Museum. In the smallest the 

 two palatine patches are close together and the posterior patches much larger in 

 proportion. 



19. Selenaspis passany (Cuvier and Valenciennes). (Plate VII, fig. 2.) 

 Bagrus passany Cuvier and Valenciennes, Hist. Nat. Poiss., XIV, 1839, 458 

 (Cayenne). — Muller and Troschel, in Schomburgk, Reisen, III, 1848, 627 

 (Waini and Barima). 



