PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 549 



Body comparatively elongate, the caudal peduncle rather longer and 

 slenderer than in H. nuchalis, and the back somewhat more elevated at 

 base of dorsal. From the insertion of the first ray of dorsal the profile 

 is more rapidly declined both anteriorly and posteriorly than iu H. nu- 

 chalis. 



Head small and rather low, evenly rounded above. Snout short, 

 rather less obtuse than in H. nuchalis, 4^ in head. Eye large, larger 

 than in nuchalis, longer than snout, 3§ in head. Premaxillaries in 

 front higher than in nuchalis, on the level of the lower part of pupil. 

 Maxillary a trifle longer than in H. nuchalis, not quite reaching to eye, 

 its length about 5^ in head. Mouth rather more oblique than in H. 

 nuchalis, the lower jaw scarcely shorter than the upper when the mouth 

 is closed. Lower jaw rounded, slightly less obtuse than in H. nuchalis. 

 Suborbital bones very narrow, much narrower than in H. nuchalis or 

 S. argyritis (somewhat variable in all three species), the anterior sub- 

 orbital about three times as long as deep. In H. nuchalis it is usually 

 not twice as long as deep. Scales, lateral line, and fins essentially as in 

 H. nuchalis, the dorsal rather higher, its anterior rays as long as head. 



Color, bluish above, silvery below, a silvery lateral shade. Finsi^ale. 



Alimentary canal (according to Hay) shorter than in H. nuchalis ; 4J 

 to 7^ times length of body. 



Length of largest specimen, about 4 inches. 



Specimens of this species have been sent to the National Museum by 

 Professor Hay, from Memphis, Tenn., and from Vicksburg, Edwards, 

 Jackson, Vaughans, and Grenada, Miss. No. 32306, from the Pearl 

 River, at Jackson, may be regarded as the special types of the species. 



Of Hylognathus nuchalis, I have examined many specimens from the 

 Delaware Eiver, and from various streams in Indiana, Illinois, Kentucky, 

 Tennessee, Alabama, Mississippi, Iowa, Kansas, Wyoming, Missouri, 

 Arkansas, anii Texas. The only variations I notice in these may be thus 

 summarized : Certain Iowa specimens ( Des Moines R. ; Hundred and 

 Two River) are dusky in color, instead of the usual bluish-silvery shades. 

 Some Alabama specimens have the eye larger, almost as large as in H. 

 hayi. In other specimens, from Kansas, from the Missouri River (Saint 

 Joseph), and from the Arkansas River (these the types of Hyhognathus 

 placitus Girard), the eye is smaller (4 to 4J in head) and there are some 

 slight differences in proportions, the caudal peduncle being less slender, 

 &c. These possibly represent a distinct subspecies, or even species 

 {placita), but I think that a full series will show complete intergradation 

 with H. nuchalis. The suborbitals are alike in both, as also in all the 

 real and supposed species of Hyhognathus., excepting H. hayi. Specimens 

 from the Potomac are larger in size (6 inches or more) than any others 

 I have ever seen. These are also less elongate than the Western speci- 

 mens, and the eye is proportionately larger (3f in head). Otherwise I 

 can detect no difference. These specimens represent the Hyhognathus 

 regius of Girard, which for the present we may regard as a distinct sub- 



