1856.] 185 



We begin the group with the genus 



Argyreus, Heck. 



which is the exact synonym of Agassiz's Rhinichthys. And we are not a little sur- 

 prised at seing the learned Professor bring forward his generical appellation,* 

 introduced into the nomenclature in 1850, in preference to that of Heckel insti- 

 tuted in 1840, especially when elsewhere he appears so eager at restoring all 

 such names as have the priority of publication, and which is nothing but just. 

 The natural characters of the genus Argyreus, are : " A snout more or less 

 protruding beyond the lower jaw, thus giving the mouth an inferior position." 

 In that respect it resembles Cainpostoma and similar Chondrostomi. " The mouth 

 itself is rather small, surrounded with quite narrow and smooth lips," covered 

 with a deciduous cartilaginous pellicle in the western species, "and provided 

 upon its angle with a small barbel, sometimes very conspicuous." The gill open- 

 ings are separated beneath by a very wide isthmus. The insertion of the ven- 

 trals is situated in advance of the anterior margin of the dorsal fin, which is 

 higher than long. The caudal is furcated. The scales are small. The pharyn- 

 geal bones are quite narrow, and stouter above than below. The teeth are of 

 the hooked type without grinding surface, strongly hooked and disposed thus : 

 1 I 4 4 I 2, that is, upon two rows, four in the outer row, and one or two in the 

 inner row. 



The following species have already been mentioned : 



1. Arygreus ATEONAS0S, Hcck. See Storer, Hist, of Fish, of Mass. in 

 the Mem. of the Amer. Acad, new ser. vol. v. 1855. 



2. Argyreus nasutus, Grd. See Storer, Hist, of Fish, of Mass. in the 

 Mem. of the Amer. Acad. v. 1855. 



3. Arygreus marmoratus. Rhinichthys mormoratus , Agass. Lake Sup. 1850, 

 354, PI. ii. figs. 1 and 2. 



From Sault St. Mary. L. Agassiz. 



4. Argyreus obtusus. Rhinichthys obtusus, Agass. Amer. Journ. of Sc. 2d. 

 fier. xvii. 1854, 357. 



From Tennessee River. 



5. Argyreus meleagris. Rhinichthys meleagris, Agass. Amer. Journ. of Sc. 

 2d. ser. xvii. 1854, 357. 



From Iowa. 



To which we add, as new : 



6. Argyreus dulcis. It has the snout more prominent than .4. aironasus,a.n6. 

 less so than A. 'nasutus. The head is well developed, constituting the fourth of 

 the length, the caudal fin excluded. The eye is quite small and subcircular, its 

 horizontal diameter entering six times in the length of the side of the head, a 

 little over twice in advance of its anterior rim. The mouth is larger than in most 

 of its congeners, and the barbel much more conspicuous. The dorsal fin, as usual, 

 is higher than long, but its upper margin is slightly convex. Its anterior 

 margin is nearer the extremity of the snout than to the insertion of the caudal 

 fin. The latter constitutes a little less than the fifth of the entire length. The 

 anal is a little shorter than the dorsal, but not as deep as the latter is high. 



D 10 ; A 9 ; C 4, 1, 9, 8, 1, 5 ; V 8 ; P 13. 



The dorsal region is greyish yellow ; the sides yellowish, with an indistinct 

 silvery band ; beneath yellowish white. The dorsal region, including the upper 

 part of the flanks, is spread over with black specks, sometimes observed beneath 

 the silvery band also. 



Specimens, the largest of which measuring about three inches and a half, 

 were collected by the late J. S. Bowman, in the Sweet Water, a tributary stream 



* Amer. Journ. of Sc. 2d. ser. xvii. 1854, 357. 



