SOUTH AMERICAN NEMATOGNATHI. 455 



bridge. Barbels reaching beyond the base of the ven- 

 trals. Lateral plates low, not nearly covering the entire 

 sides; nuchal plates rudimentary, almost the entire 

 nuchal region naked. This is undoubtedly the form de- 

 scribed by Hensel as hemiphractits. 



445. Callichthys arcifer. 



CalUchthys arcifer Heusel, Wiegiu. Archiv. 1868, i, 373 (Kio de 



Janeiro.) 

 Cataphractus arcifer Eigeum. & Eigenm. Proc. Cal. Acad. 2d Ser. i, 



164, 1888 (name only.) 

 Habitat: Rio Janeiro. 



XCVII. HOPLOSTERNUM. 



Callichthys Cuv. & Val. Hist. Nat. Poiss. xv, 1840 ^sp). 



Boplosternum Gill, Syn. Fish. Trinidad, 35, 1858 

 {lcevigatuin=:littorale). 



Type: Galliehthys Icevigatus Valenciennes. 



Habitat: Rio Plata to Trinidad and Rio Huallaga. 



The exposure of the coracoid process would hardly be 

 sufficient to separate this genus from Gataphractas, but 

 the structure of the anterior portion of the coracoid 

 bone in H. littorale and G. callichthys differs also. 



ANALYSIS OF THE SPECIES OF HOPLOSTERN0M. 



a. A series of azygous plates extending from the adipose fin forward to the 

 dorsal fin; coracoid processes not entirely covering the breast; a rather 

 broad, truncate occipital process; margins of the first pair of nuchal 

 plates parallel with those of the second in the young, rounded in the 

 adult; no barbels on the chin, the inner rictal barbels reaching beyond 

 base of ventrals. littorale 446. 



aa. A series of azygous plates extending from the adipose fin forward part 

 way to the dorsal fin. 



b. Occipital bone pointed in front, entering as a wedge between the 

 frontals to the fontanel; head broad, depressed; azygous plates about 

 7; caudal truncate or rounded; lower lip very broad; dorsal fin with 

 a strong flat spine. thoracatum 447 . 



bb. Occipital bone truncate in front, not reaching the fontanel; i^rofile 

 steep; azygous plates 5; caudal emarginate. Head depressed, snout 

 broadly rounded; lower li^j little reverted, without barbels; inferior 



