214 ON THE DISTRIBUTION OF FRESH-WATER FISHES 



those from the Holston River. There is more than one strongly marked variety of 

 this species, which, with variations attributable to age, has given rise to several 

 synonyms. 



Var. I. nigromaculata Girard (Esirella). 



Head 4'5 times in length ; dorsal and thoracic regions scaled ; 14 rays in second 

 dorsal ; a black spot at basis of first dorsal, and Jilack bar below orbit. Potomac 

 River. 



Var. II. olmstedi. 



Head four times in length of body ; second dorsal radii 14 ; no black spot on 

 first dorsal and bar below orbit. 



Many specimens of this variety from many eastern localities. Of forty specimens 

 from Crosswicks, N. J., but one, the largest, has scales on the dorsal and thoracic 

 regions ; it is otherwise identical. 



Var. III. brevipinnis. 



Only 12 rays in the second dorsal fin ; head four times in length ; dorsal blotches 

 reduced to punctse, and the lateral to zig-zags, back punctate between ; no spot at 

 base dorsal. 



a. A black bar below eye ; two speciuiens fro:n the Holston; they have the dorsal 

 region scaly and the thoracic smooth. 



««. No black bar below orbit ; 18 — 20 specimens from the Kiskiminitas, Penn. 

 A.11 have the dorsal and thoracic regions smooth. 



HYOSTOMA Agass. emend. 



The characters assigned to this genus by Agassiz have not seemed to the writer to 

 distinguish it sufliciently from PoeciUcJithys of the same author. Its physiognomy is, 

 however, somewhat peculiar, and on examination I find it to be distinct in the 

 absence of vomerine teeth. 



I. Branchiostegals broadly connected across the pectoral region. 

 a. Operculum and cheeks scaled. 

 fi. Dorsal spines fourteen to twelve. 

 Body elongate; head abruptly obtuse, mouth slightly inferior; 

 dorsal rays xiv. 13; scales J§ ; a series of brown U-shaped 

 marks below lateral line; dorsal fin red in the middle, and a 



black spot before and behind, blennioperca. 



Body elongate ; head abruptly obtuse, mouth slightly inferior ; dor- 

 sal rays xii (I). 13 ; scales ^^ ; scaled in front of dorsal fin ; 

 brown U-shaped marks below the lateral line, and numerous 

 zig-zag lines above it, CTMATogeammum. 



