178 [September, 



4. DioNDA PAPALis. The head in this species is rather small, but rounded off 

 upon the snout ; it forms a little less than the fifth of the entire length. The 

 body is thlckish anteriorly, subcylindrical, tapering posteriorly. The dorsal 

 and anal are proportionally well developed. The caudal is forked ; the ventrals 

 are inserted under the anterior margin of the dorsal. The scales are large. The 

 coloration has been altered to a uniform black subsequently upon its immersion 

 in alcohol with sundry other specimens. 



Collected in Delaware Creek, a tributary of the Rio Pecos, and brought home 

 by Capt. John Pope, U. S. A. 



5. DioNDA ARGENTOSA, has a small head and obtuse snout, a rather slender 

 and compressed body. The head constitutes 2-llths of the total length. The 

 insertion of the ventrals is situated opposite the anterior margin of the dorsal. 

 The scales being quite large, the lateral line is slightly deflected upon the thorax. 

 Color of the dorsal region reddish brown ; sides and abdomen as if painted over 

 with silver or quicksilver. Fins olivaceous. 



Collected in San Felipe Creek and Devil's River, two tributaries of the Rio 

 Grande del Norte (Rio Bravo), by John H. Clark, under Col. J. D. Graham, 

 U. S. A. 



6. DiONDA CHRYSiTis. Very slender and compressed ; head very small and 

 obtuse, contained six times in the total length. Eyes large and circular. Origin 

 of ventrals opposite the anterior margin of dorsal. Upper surface of head tuber- 

 culous. Scales large. Dorsal region reddish brown ; sides and abdomen as if 

 painted with gold. A black spot upon the base of the caudal fin. Fins them- 

 selves yellowish or olivaceous. 



Specimens were collected by John H. Clark, under Col. J. D. Graham, U. S. A., 

 in Live Oak Creek, presumed tributary of Rio Pecos, or else losing itself into 

 the ground. 



T. DiONDA MELANOPS. A rather short and deep body characterizes this 

 species. The head is proportionally well developed, forming a little less than 

 the fifth of the total length. The snout is conical and not abruptly truncated. 

 The insertion of the ventrals is situated a little posteriorly to the anterior margin 

 of the dorsal. Scales large. The dorsal region is blackish ; the sides and abdo- 

 men are dotted with black upon a bluish lead ground, giving the whole fish a 

 dark appearance. A black spot upon the base of the caudal fin. 



From Buena Vista, Coahuila ; collected by Lieut. D. N. Couch, U. S. A. 



8. DiONDA concHi. Though closely allied to the preceding, it may readily be 

 distinguished from it by a more elongated body and more elongated head. The 

 snout is rounded. The eye is circular and of medium size. The ventrals are 

 inserted posterior to the anterior margin of the dorsal. The scales are quite 

 large. Upper regions greyish black; sides and abdomen yellowish or whitish, 

 either unicolor or maculated. A black spot upon the base of the caudal. 



Specimens collected by Lieut. D. N. Couch, U. S. A., at Guajuco, Monterey 

 and Cadereita, New Leon, in the waters of the Rio San Juan. 



9. DiONDA PLUMBEA. Bcsidcs scvcral other peculiarities of structure, this 

 species may be distinguished from all its congeners by the size of its scales, 

 which are the smallest in the genus. 



Greyish above, whitish or yellowish white beneath. Black spot at base of 

 caudal. 



Collected in the head waters of the Canadian River (Llano Estacado), by H. 

 B. MoUhausen, under Lieut. A. W. Whipple, U. S. A. 



10. DiONDA SPADiCEA. This has the general aspect of D. plumhca, in being 

 slender and elongated in body and head. The latter, however, is more conical 

 and the eye smaller, the scales being but a very little larger. Colors brownish 

 red above, whitish beneath. No spot at the base of the caudal. 



From Fort Smith, Ark. ; collected by H. B. MoUhausen, under Lieut. A. "W. 

 Whipple, U. S. A. 



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