

SYNOPSIS OF THE CYPKINIDJE OF PENNSYLVANIA. 



369 



matter, as has been shown by Prof. Peters, is deposited in little sacs of the derm (chroma- 

 tophoras) ; these may be made to disclose their crimson contents by means of a sharp in- 

 strument, some time after the fish appears to have lost his livery. The strengthening of 

 the pectoral rays is appropriate to the increased exertion incident to the impregnation of 

 the eggs. Later in the season the brilliant crimson gives place to orange, which fades to 

 golden ; this may often be seen in specimens caught as late as the end of summer, when 

 many have resumed their silver white. 



This species is abundant in the rivulets tributary to the three great rivers that drain 

 our State. A Northwestern representative, the R. lunatus, will perhaps be found also 

 within our limits. 



Argyreus atronasus is a favorite for aquaria, and is generally sold as the " black-nosed 

 dace." 



ARGYREUS NASUTUS, Ayres. 



Boston Journ. Nat. Hist., Girard. Proc. Acad., Phila., 1. c, 1856. 

 Rhinichthys, Agassiz. Chondrosloma, Heckel, Fische Syriens. 



This is a larger and more elongate species than the last, with a most 

 prominent and flattened muzzle. 



It is of a general olivaceous color, paler below, with numerous brown punctulations, sometimes extending over 

 the sides of the belly, and almost blackening the upper surfaces, and in young specimens accumulated near the 

 lateral line. There is never seen the lateral band of the atronasus, and the space between the orbit and mujzzle is 

 blackish like the top of the muzzle and front. There is a black spot on the operculum. In spring the lips and 

 parts of cheek of the males, with the paired fins and the caudal, are of a bright crimson. The pectorals of both 

 sexes are lanceolate, but as in the last species, the males have the rays much enlarged ; these fins are absolutely 

 longer in this sex, attaining the ventrals, while in the females they reach only two-thirds that distance. Radial 

 formula as in the preceding species, D. I. 8, A. I. 7, P. 15. Lateral commencing at top of operculum, decurved; 

 scales in a Delaware specimen 14 — 65 — 8, in two Susquehanna, 12 — 57—7-8; the latter wore rather smaller. 



This species is less abundant than the last, and appears to be rather local in Eastern 

 Pennsylvania ; it prefers boisterous and rocky streams, in whose rapids and ripples it may 

 be seen in twos and threes, and will sometimes take the hook with the spring and energy 

 of a trout. I have taken this fish several times in the tributaries of White Clay Creek, 

 Chester County, and have it from the neighborhood of Safe Harbor, Lancaster County, 

 on the Susquehanna. The latter specimens are almost black above and on the sides. It 

 is not known to occur in any tributaries of the Ohio. 



I have found a species of Entomostracous crustacean, an Argulus, parasitic on this 

 species, attached within the nareal cavity, and spread round its margin externally. J. 

 vol. xi ii — 17 



