296 ME. C. TATE REGAN ON THE 



snout, and with only a few large plates on the abdomen, in a single series between the 

 lateral series, which are formed by 4 plates on each side. Olivaceous ; fins, except 

 the anal, with small dark spots. 



Rio Cujaba, upper course of the Rio Paraguay. 



12. Hemiodontichthys. 



Hemiodon (non Swainson) Kner, Denkschr. Ak. Wien, vi. 1854, p. 89. 



Hemiodontichthys Bleck. Ned. Tijd. Dierk.i. 1863, p. 81 ; Eigenrn. & Eigcnm. Proc. Cal. Ac. (2) ii. 

 1889, p. 34, and Occ, Pap. Cal. Ac. i. 1890, p. 359. 



This genus is distinguished from Loricaria by the snout with a long narrow rostrum, 

 and by the absence of teeth in the upper jaw. The rather short barbel, the papillose 

 lower lip with short marginal fringes, and other characters seem to indicate relation- 

 ship with Loricaria lima and its allies. 



Key to the Species. 



Rostrum without anterior expansion 1. H. depressus Kner. 



Rostrum with an anterior expansion, armed with recurved spines . . 2. H. acipenserinus Kner. 



1. f Hemiodontichthys depressus. 



Hemiodon depressus Kner, Denkschr. Ak. Wien, vi. 1853, p. 91, pi. vii. fig. 1. 

 Loricaria depressa Giinth. Cat. Fish. v. p. 259 (1864). 



Length of head 3^-3-^ times in the total length. Head If times as long as broad. 

 Diameter of eye about 7-f times in the length of head and equal to the interorbital 

 width, length of snout ~\\ times. Head strongly depressed, without keels or ridges ; 

 orbit with a broad shallow notch ; snout with a long, flat, narrow process, anteriorly 

 rounded ; anterior lip short, the posterior covered with small papillae, with short 

 marginal fringes ; barbels short ; teeth small in the lower jaw, absent in the upper. 

 27 scutes in a longitudinal series, 13-14 + 13-14; lateral keels separate throughout, 

 the lower the stronger ; scutes otherwise not keeled ; abdomen with some large 

 irregularly arranged plates ; lower surface of head and thorax covered with small 

 plates. Pectoral spine nearly reaching base of ventral ; upper caudal ray produced. 

 Upper part of head and body with small dark spots ; similar spots on dorsal and 

 pectoral fins. 



The typical example described by Kner is about 160 mm. long. 



Rio Negro, a northern tributary of the Middle Amazon. 



2. Hemiodontichthys acipenserinus. 



Hemiodon acipenserinus Kner, Denkschr. Ak. Wien, vi. 1853, p. 92, pi. vii. fig. 2. 

 Loricaria acipenserina Giinth. Cat. Fish. v. p. 260 (1864). 



Hemiodontichthys acipenserinus Bleek. Ned. Tijd. Dierk. i. 1863, p. 81; Eigenm. & Eigenru. Proc. 

 Cal. Ac. (2) ii. 1889, p. 34, and Occ. Pap. Cal. Ac. i. 1890, p. 359. 



