niSTOEY OF THE FISHES OF MASSACHUSETTS. 287 



The pectorals arise beneath and just anterior to the posterior angle of the oper- 

 culum. 



The ventrals, which are fin-shaped, arise opposite the origin of the dorsal fin. They 

 are not as high as the pectorals. 



The anal fin arises opposite the posterior extremity of the dorsal fin when it is 

 closed ; it is similar in form to the dorsal. Its first two rays are simple, the remainder 

 multifid. The first ray bears the same proportion to the length of the second, as the 

 first ray of the dorsal to its second ray. 



The caudal fin is large, deeply forked. The height of its middle rays is equal to 

 half the height of the outer rays. Width of the tail at extremities when expanded, to 

 height of middle rays, is as three to one. 



The fin rays are as follows: — D. 9-10. P. 16-17. V. 8. A. 9 - 10. C. 

 20 — 22, 



Length, fourteen inches. 



Remarks, This beautiful species is found in many of our rivers, and is known under 

 the names of Eoach, Dace, Chivin, and Cousin Trout. It attains the length of about 

 fourteen inches, although the specimens usually met with are much smaller. 



GENUS V. ARGYEEUS, Heck. 



General physiognomy resembling that of Catostomus. Snout more or less protru.d- 

 ing beyond the upper jaw, thus giving the mouth an inferior position. The month 

 itself is rather small, bordered with quite narrow and smooth lips, and provided at its 

 angles with a small barbel, not always easily recognizable, especially in immature 

 specimens preserved in alcohol. The pharyngeal teeth are disposed upon a double 



row. 



This character of a barbel at the angle of the mouth, as well as the structure of the 

 lips and the disposition of the ventral fins, which are inserted in advance of the anterior 

 margin of the dorsal, indicates in these fishes a much greater affinity with Cheilonemus 

 than with Catostomus. Indeed, the only conspicuous generical differences which can be 

 traced between Argyreus and Cheilonemus consist in a more cylindrical body and very 

 small mouth in Argyreus^ and the tendency of the snout to elongate and project in 

 some instances considerably beyond the jaws. 



