32 



UNITED STATES AND MEXICAN BOUNDARY. 



The dorsal region is bluish, tinged with green or olive ; the flanks being silvery and the belly 

 of an opaque white. The fins are uniform greyish olive, the adipose alone being blackish. 



List of specimens. 



Catal. 



No. 



No. of 



spec. 



Age. 



835 



1 



Adult.. 



Locality. 



Indianola, Texas 



When 

 collected. 



1851 



Whence obtained 



Nature of 

 specimen. 



Col. J. D. Graham. . 



Alcoholic 



Collected by 



Jno. H. Clark 



ARIUS EQUESTRIS, B. & G. 



Plate XV. 



Spec. Char. — Head contained four times and three-quarters in the total length. Horizontal diameter of the eye contained 

 five times in the length of the side of the head. Maxillary barbels extending to the middle of the length of the pectorals. 

 Anterior margin of the dorsal fin thrice as high as its posterior margin, and equidistant between the extremity of the snout 

 and the adipose ; its superior margin being sub-concave. Adipose dorsal fin of medium size, and situated opposite the middle 

 of the anal. The latter is deeper than long, and concave upon its outer edge. Extremities of the pectorals extending as far 

 back as the posterior margin of the dorsal. Ventrals are nearly equidistant between the tip of the pectorals and the origin of 

 the anal. 



Syn. — flrfctl equestris, B & G. in Proc. Acad. Nat. Sc. Philad. VII, 1854, 26. 



The color is of a greyish argentine hue, somewhat darker along the dorsal region than on 

 the flanks and the "belly. 



Br. V: V; DIJ; A 16; C 13, 1, 7, 7,1,12; V6; PI, 9. 

 Plate XV, fig. 1, represents Arius equestris, size of life ; fig. 2 is an outline of the fish seen 

 from above ; fig. 3, an outline of the head seen from beneath, showing the shape of the mouth 

 and the insertion of the mental barbels. 



List of specimens. 





Catal. No. of Age. 



No. 



836 



spec 



1 



Adult.. 



Locality. 



Indianola, Texas 



When 

 collected. 



Whence obtained. 



1851 



Col. J. D. Graham. . 



Nature of 

 specimen. 



Collected by 



Alcoholic. Jno. H. Clark 



1. PIMELODUS AFFINIS, B. & G 



Plates XVI & XVII. 



Spec. Char.— The head is contained five times and a half in the total length, in which the caudal fin enters but five times. 

 The eye is of medium size, its diameter entering a little more than six times in the length of the side of the head. The anal 

 is very elongated, its base being somewhat more than the fourth of the whole length, and the tips of its posterior rays extend 

 further back than the extremity of the adipose fin, which is inserted opposite the posterior third of the one just alluded to. 

 The extremity of the pectoral fins extends nearly as far as a vertical line drawn at the posterior margin of the dorsal ; the fins 

 themselves being rather slender. The ventrals are broad, somewhat shorter than the pectorals, and extend beyond the anterior 

 margin of the anal. 



Syn.— Pimelodus affinis, B. & G. in Proc. Acad. Nat. Sc. Philad. VII, 1854, 26. 



t> 



from 



more advanced position of the dorsal fin, and a greater elongation of the barbels : the maxillar 



