44 



UNITED STATES AND MEXICAN BOUNDARY 



5. DIONDA MELANOPS, Grd. 

 Plate XXVI, Figs. 17—20. 



£p£c. Char. — A rather short and deep body characterizes this species. The head is proportionally well developed, forming 

 less than the fifth of the total length. The snout is conical and not abruptly truncated. The insertion of the ventrals is situ- 

 ated somewhat posteriorly to the anterior margin of the dorsal. Scales large. The dorsal region is blackish ; the sides and 

 abdomen 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. 



Syn. — Dionda melanops, Grd. in Proc. Acad. Nat. Sc. Philad. VIII, 1856, 178. 



Plate XXVI, fig. 17, represents Dionda melanops, size of life; fig. 18 is a scale from the 

 dorsal region ; fig. 19, a scale from the lateral line ; fig. 20, a scale from the abdominal region. 



List of specimens. 



Catal. Cor. No No. of 



No. of teeth 



38 



'2652 



Locality 



s 



pec 



When 

 collected. 



Whence obtained. 



Nature of 

 specimen. 



Collected by 



5 



Kuena Vista, Coahuila 



1853 



Lieut. D. N. Couch.. 



Alcoholic . . Lieut. Couch 



. • 6. DIONDA COUCEI, Grd. 



Plate XXVI, Fias. 1—4. 



Spkc. Char. — 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. 



Syn. — Dionda couchi, Grd. in Proc. Acad. Nat. Sc. Philad. VIII, 1858, 178. 



Plate XXVI, fig. 1, represents Dionda coucM ', size of life; fig. 2, a scale from the dorsal 

 region; fig. 3, a scale from the lateral line ; and, fig. 4, a scale from the abdominal region. 



List of specimens. 



Catal. Cor. No. 



No. of teeth. 



_ 



40 

 41 

 42 



2654 

 :2G55 



N0.0I 



spec. 



Locality. 



4 

 5 



4 



Guajuco, New Leon 

 Monterey, N. L. ... 



• * « 



Cadercita, N. L 



When 

 collected 





Whence obtained. 



Nature of 

 specimens. 



1853 

 18:3 

 1853 



Lieut. D. N. Couch 



do 



Collected by 



Alcohoiic . . Lieut. Couch 



do 



do 



do 



do 



do 



ALGOMA, Girarcl. 



Gen. Char. — Partakes, in a measure, of the characters of Hyborhynchus and Pimcpfiales. The teeth are of the cultriforra 

 kind, of the grinding type, disposed upon a single row of four: 4 — 4. The grinding surface is nearly linear, in which respect 

 the teeth resembJe more those of Pimephales than of Hyborhynchus. The pharyngeal bones do not differ materially in these 

 genera. The head is small and sub-truncated, the mouth small, with the lower jaw shortest, and overlapped by the upper, a 

 feature also noticed in Hyborhynchus. The isthmus is of a moderate size ; the eye well developed. The insertion of the ventral 

 takes place posterior to the anterior margin of the dorsal. The latter is higher than long, without a short and thick ray 

 nteriorly . The anal is shaped like the dorsal. The caudal is furcated. The scales are large, and deeper than long, furrowed 

 upon the posterior section only ; the lateral line sub-median, is slightly deflexed upon the abdomen. 



Syn.— Algoma % Grd. in Proc. Acad. Nat. Sc. Philad. VIII, 1856, 180. 



The large scmL will serve to 

 II rlyiulns ami Pmwphah r. 



distinguish, upon a first glimpse, this genus from both 



