HADROPTERUS BLACK-SIDED DARTERS 285 



Our single specimen of this species was taken at Havana, 

 Illinois, in the summer of 1897. While presenting resemblances 

 to both H. aspro and P. caprodes, it may be readily distinguished 

 from both by its different color pattern. 



Described from Lake Tippecanoe, Indiana. 



Nelson, 1876, Bull. 111. State Lab. Nat. Hist., I. 1, 35 (Etheostoma). 

 J. & G., 501 (Alvordius); M. V., 127 (Etheostoma); B., I, 63 (Percina); J. & E., 

 I, 1030; J., 39 (Alvordius); F., 65; L. 27. 



Length 3 inches; body moderately elongate and compressed; form 

 distinctive among darters for its graceful outlines, the back gently elevated 

 and the anterior portion of the body faultlessly tapered to the end of the 

 slender pointed head; depth 5.4 to 6.2 in length; greatest width of body 

 about % of its depth; depth caudal peduncle 1.8 to 2.4 in its length. Color 

 yellowish brown, more or less marbled, blotched, and tessellated with darker, 

 but the colors generally duller than in H. aspro; sides with about 12 or 13 

 more or less indefinite dusky blotches, sometimes confluent into a monili- 

 form band, in instances fading so as to become almost imperceptible; back 

 with tessellations and upper portion of sides with marblings of dark color, 

 ordinary examples having a vermiculated appearance; first dorsal with a 

 broad band of orange-red across its middle and with narrow outer edging of 

 pale blue, the hues much more brilliant in males than in females; second 

 dorsal and caudal faintly barred; other fins plain, the anal and ventrals 

 dusky in males; a dark band from front of orbit through nostril to end of 

 snout; vertical streak below eye faint. Head long, slender and quite pointed, 

 3.6 to 3.9 in length; width of head 2.1 to 2.4; interorbital space extremely 

 narrow, 6.7 to 7.9 in head; eye 3.8 to 4.5; nose pointed, 3.5 to 4 in head; 

 mouth moderate, maxillary reaching a little past front of orbit, the cleft 3.4 

 to 4 in head; jaws nearly equal; gill-membranes free from isthmus and broadly 

 connected, the distance from muzzle to their free posterior margin 1% to 

 1^2 times that to back of orbit. Dorsal fin XII or XIII, 12-14; spinous and 

 soft portions scarcely separated at base; height of first dorsal 2.2 to 2.9 in 

 head, second 1.7 to 2.1 (height of first 70 to 88 per cent, of second); caudal 

 slightly emarginate; anal II, 8 or 9, rarely 10 or 11; pectorals 1.2 to 1.4 in 

 head; separation of ventrals slightly less than their width at base. Scales 

 8-10, 64-69, 10-12 [12-18]; usually no pores lacking; cheeks covered with 

 very fine scales, in 14 or 15 rows; opercles and nape scaled; breast naked or 

 with a median large caducous shield; mid-ventral line with small caducous 

 plates. 



This modestly colored but shapely darter is distributed 

 much like Percina caprodes, except that we have not found it in 

 the northern glacial lakes, and that it is dispersed more widely 

 through the smaller streams. It has occurred in ninety-five of 

 our collections, most abundantly in the Illinois basin, but fre- 



