38 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



ff. Fontanelle acute posteriorly, prolonged in a groove; shields finely gran- 

 ular ; barbels rather long; caudal more than two-thirds 

 head ; head 4 iu length Insculptus, 7. 



ee. Interorbital space flat and smooth, a triangular smooth area extending 



backward from it. 

 (j. Groove of fontanelle almost obsolete, not reaching occipital process; 

 occipital process about as broad at base as long, its 

 margins concave; caudal a little shorter than head; 

 head 3J in length ; shields of head rather coarsely gran- 

 ular Planiceps, 8. 



gg. Groove of fontanels well defined, reaching occipital process ; occipital 

 process longer than broad, its margins straight ; barbels 

 short, compressed at base ; caudal as long as head ; head 

 long, 3£ in length, its shields finely granular ; pectorals 

 and ventrals sometimes black at base.PLATYPOGOX, 0. 

 dd. Vomerine bands of teeth separated on the median line * ; fontanelle prolonged 



backward in a groove ; interorbital area with smooth 

 ridges. 

 h. Mouth large, its breadth half or more length of head; spines low, 

 less than two-thirds head ; head large, 3| in length. 



Elatturus, 11. 



hh. Mouth small, its breadth much less than half head ; spines high, 

 not much shorter than head ; caudal nearly as long as 



head ; head small, 4 in length Oscultjs, 12. 



aa. Bands t of palatine teeth, without backward prolongation on the inner margin; 



vomerine bands of teeth not confluent; ante-dorsal 

 shield small, crescent-shaped; species mostly with blue 

 luster in life, 

 i. Eyes placed well above level of angle of mouth. 

 j. Teeth on vomer and palatines villiform or bluntly conical, not 

 granular. (Hexaiiematiehtliyst Bleeker.) 

 k. Interorbital area flattish and smooth, without ridges or granu- 

 lations ; fins not low, the spines more than half head; 

 gill- membranes not meeting in an angle. 

 1. Fontanelle prolonged backward as a narrow groove. 

 m. Inner edge of bases of paired fins jet-black ; occipital 

 process short, less than one-third head. 

 u. Occipital process emarginate at tip ; bands of palatine 

 teeth moderate (varying with age); harbels rather 

 short; head 3^ in length Assimilis, 13. 



mi. Occipital process truncate at tip; bauds of palatine 

 teeth small, not twice as large as vomerine bands; 

 barbels rather long ; head 3§ in length. 



CiERULESCENS, 14. 



mm. Inner edges of paired fins pale; occipital process long, 

 its length about one-third head, its tip convex; head 

 3f in length Felis.§ 



*This character varies somewhat with age, and may prove unreliable. 



tThis character has not been verified in ccerulescens, mclavopus, and fiirthi. 



{ = Notarius, Leptarius, and Jriopsin Gill. 



$ SiluruB fclis L. Syst. Nat: Jrins miVberti Cnv. & Yal. xv, 74: Arius equestrie 

 B. A: G. Proc. Ac. Nat. Sei. Phila. 1855, 26. Cape Cod to Texas; everywhere very 

 abundant along the Atlantic coast of the United States. 



