1856.] 193 



Amongst the few genera which seem to be common to both hemispheres, there 

 is the genus 



Alburnus, Rond. 



which we find distributed over a large portion of our continent. But, in order 

 to include the American species in that genus, the diagnosis is to be slightly 

 modified, so as to read : Raptatorial teeth disposed upon a double row of two and 

 four or five, thus: 2 | 5 5 | 2 or 2 | 4 4 | 2. la all the species which I have 

 examined, the teeth are disposed according to the second formula. 



The teeth themselves are slender and compressed, more or less hooked. The 

 pharyngeal bones are slender, expanded upon their convexity, the upper limb 

 bent inwards and downwards, and the inferior limb rather exiguus and shorter 

 than the upper. Should the American species, now referred to this genus, prove 

 generically distinct upon a more minute comparison, which we cannot now estab- 

 lish, the name of Alburnellus might unite them under a new generic appella- 

 tion. 



1. Alburnus dilectus, is about three inches and a half in total length ; the 

 head forming a little less than the sixth part of it. The greatest depth is nearly 

 equal to the length of the head. The diameter of the circular eye is contained 

 a little more than three times in the length of the side of the head, and less 

 than once in advance of its anterior rim. There are ten longitudinal rows of 

 scales between the insertion of the ventrals and the base of the dorsal. The 

 lateral line is upon the fourth row from the ventrals upwards. The color is 

 uniform yellowish red with a lateral silvery streak. 



Collected in the Arkansas river near Fort Smith, by Dr. Geo. G. Shumard. 



2.^Alburntjs umbratilis, is a shorter and deeper species, and which migh* 

 easily be taken for a Lnxilus, so striking is its general resemblance with smal^ 

 specimens of the latter genus. The greatest length is about three inches ; the 

 greatest depth being equal to the length of the head, and contained five times 

 in the total length. The lateral line, though running along the fourth row of 

 scales from the insertion of the ventrals, is more deflexed upon the abdomen 

 than in A. dilectus; the longitudinal rows of scales being fourteen in number. 

 The ground color is silvery grey above; the back, sides and fins as if shaded ; 

 the belly reddish. 



Specimens were collected, by H. Miillhausen, in Sugar Loaf Creek, a tributary 

 to Poteau river, flowing into the Arkansas near Fort Smith. 



3. Alburnus amabilis This is a very slender and graceful species, about 

 two inches and a half in total length. The head constitutes the fifth of the 

 length, and the greatest depth, the sixth. There are nine longitudinal rows of 

 scales upon the flanks, between the insertion of the ventral fins and the dorsal 

 line. The lateral line, as usual, is found along the fourth row from the ventrals 

 upwards. The color is dark reddish brown, silvery upon the flanks. A black 

 patch upon the base of the tail. 



Specimens were collected in the Rio Leona, an affluent of the Rio Nueces, by 

 John H. Clark, under Col. J. D. Graham, U. S. A. 



4. Alburnus meqalops. Resembles A. amabilis in general traits, being slender 

 and graceful, but easily distinguished from it by a shorter and more rounded 

 snout and a larger eye. The coloration is the same with the exception of the 

 black caudal patch, which does not exist here. The average size of the speci- 

 mens before us is about two inches. 



Caught in San Felipe Creek, Texas, by John H. Clark, under Col. Graham. 



5. Alburntts socius. Resembles A. mcgalops by its snout and eye. The total 

 length is two inches and a half, the head forming the fifth part of it. The greatest 

 depth is a little less than the length of the head. The dorsal region is oliva- 

 ceous, the flanks silvery, and the belly yellowish. Opercular apparatus golden. 



Specimens of this species were collected in Live Oak Creek, Texas, by John 

 H. Clark, under Col. J. D. Graham, U. S. A. 



15 



