238 
BULLETIN OF THE BUREAU OF FISHERIES 
head low, as broad as deep at eyes; snout rather short, decurved, 3.45 to 3.85; eye 3.4 to 3.75; 
interorbital very narrow, 11.15 to 13.6; mouth placed low, horizontal, terminal; maxillary reaching 
to or a little beyond anterior margin of eye, 2.9 to 3.25 in head; opercle ending in a strong spine; 
preopercle unarmed; gill membranes somewhat united, free from the isthmus; scales strongly ctenoid, 
covering entire body, including the chest, also present on cheeks and opercles; lateral line complete; 
dorsal fins well separated, the spines of the first slender, the longest one equal to distance from tip of 
snout to preopercular margin; soft dorsal somewhat higher; caudal fin straight to slightly rounded; 
anal fin small, its origin falling slightly behind that of soft dorsal; ventral fins moderate, inserted a 
little behind base of pectorals; pectoral fins rather long, pointed, 0.86 to 1 in head. 
Color olivaceous above; pale underneath; back with six to eight black, saddlelike blotches; 
sides with irregular dark markings; a dark bar below the eye and one in front of it; dorsal fins, caudal, 
and pectorals spotted and barred with black; anal and ventrals plain. 
Many specimens, ranging from 35 to 80 millimeters (1J^ to 3 3^ inches) in length, were preserved. 
This is the only darter taken in brackish water. The species appears to be variable and varieties 
have been recognized. The form herein described, as a matter of fact, is often considered only 
a subspecies or variety of B. nigrum, the typical form of which occurs in the upper Mississippi 
and the Great Lakes region. B. olmstedi may be recognized by the complete lateral line, the 
completely scaled chest, cheeks, and opercles, the high fins, and the more profuse and distinct 
dark markings on the body and fins. 
The stomach contents of 12 specimens taken in brackish water consisted wholly of small crus- 
taceans (principally Gammarus) and insect larvae. Specimens taken in May, 1922, are in spawn- 
ing condition. The ovary of a female 62 millimeters in length contained 340 eggs of uniform size, 
approximately 1 millimeter in diameter after preserving in alcohol. The smallest sexually mature 
female found in the collection is 43 millimeters long, and the smallest sexually mature male has a 
length of only 40 millimeters. 
The largest specimens in the collection (slightly exceeding 3 inches in length) appear to repre- 
sent the maximum size attained by the Johnny darter. This fish is generally common in clear, 
running streams, occurring also in quiet and standing waters. The writers find no mention in 
literature of its occurrence in brackish water. It was taken only at the head of Chesapeake Bay, 
where it was common in water that was slightly saline. 
Habitat . — Massachusetts to North Carolina in coastwise streams. 
Chesapeake localities. — (a) Previous records: None from brackish water. (6) Specimens in 
collection: All from the vicinity of Havre de Grace, Md. Highest salinity, Elk River, opposite 
Turkey Point, November 11, 1921, 2.23 per mille. 
Family LVIII— CENTRARCHIDiE. The fresh-water basses and sunfishes 
Body usually rather short and compressed; mouth large or small; premaxillaries protractile; 
maxillary usually with a supplemental bone, obsolete in small-mouthed species; teeth pointed, in 
bands on jaws, vomer, and palatines, rarely on tongue; opercle ending in two points, or with a 
single long flap; preopercle entire or slightly serrate; pseudobranchise small; branchiostegals usually 
6; gill membranes separate and free from the isthmus; gill rakers usually short; scales present on 
body, opercles, and cheeks; lateral line present, usually complete; dorsal fin continuous, some- 
times deeply notched, with 6 to 13 spines; anal fin large or small, with 3 to 8 spines. This family 
includes some of the best known and most important fishes of American fresh waters. Nearly 
all the species are carnivorous, and they build nests in which the eggs and young are carefully 
guarded. 
KEY TO THE GENERA 
a. Anal fin somewhat longer than the dorsal, with six spines; body and fins profusely and irregu- 
larly spotted with black Pomoxis, p. 239 
aa. Anal fin much shorter than the dorsal, with three spines. 
b. Body comparatively short and deep, strongly compressed, the depth frequently half the length, 
always exceeding one-third of the length; dorsal fin continuous, scarcely or not at all notched 
at the beginning of the soft rays. 
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