120 FISHES OF PENNSYLVANIA. 

narrow, grooved. The pectorals extend to tips of ventrals and half way to vent. 
Seales on the cheeks, gill-covers and temporal region. The sides of the body with 
nearly smooth scales, not closely placed and more or less concealed in the skin. 
Scales of the lateral line and caudal peduncle more developed than the others, Space 
in front of the dorsal thinly scaled. 
Php 10 pA las: 
Lateral line 75-80; six scales above it. The scales are thin, translucent, finely 
punctulated with black. Bluish blotches along the back and the lateral line; the 
median series united bya gilt line. The fins are pale. 
The sand darter inhabits the Ohio valley and a portion of the Missis- 
sippi valley. It runs into several varieties one of which is without 
scales on the nape and the anterior portion of the sides except on the 
lateral line. Another variety from southern Illinois, southward and 
westward, has the nape more or less closely scaled, the scales firmer and 
rougher than in the typical form and with a dark bar along the base of 
the soft dorsal. 
The species was first described by Prof. Baird from the Ohio valley, 
it reaches a length of two or three inches and is abundant in clear 
sandy streams. Its habits have been fully described in the American 
Naturalist, February, 1887, p. 86. The sand darter feeds upon insect 
larve, small crustaceans and other animals of suitable size. 
182. Etheostoma olmstedi Srorer. 
The Tessellated Darter. (Figure 67.) 
The head is contained four and one-fourth times in total length ; depth five and one- 
fourth times. The cheeks and opercles are scaly; nape and breast naked. The lat- 
eral line is complete with about fifty scales. 
104 SD. Ee ANS eS 
The color is olivaceous ; fins with many narrow bars; the back tessellated; sides 
with blotches and zigzag markings. Head in spring males black, a dark streak for- 
ward from the eye and another one downward. 
The common darter or tessellated darter is found from Massachusetts 
to Georgia. It is replaced in Cayuga Lake and some other regions 
to the southward by a black spotted variety, which differs from the 
common form still further in having the nape and breast closely scaled. 
This species grows to a length of three and one-half inches and is a 
near relative of the Johnny darter (Boleosoma nigrum) of Kafinesque. 
This darter secretes itself on the bottom in small clear brooks, swim- 
ming rapidly for a short distance when alarmed. The sexes are very 
different in appearance, the males having higher and more brightly 
colored fins than the females. The males are also larger than the females 
and in the spring are much spotted with black. 
183. Etheostoma nigrum RarinesqQue. 
The Johnny Darter. 
This is one of the small species, attaining a length of only two and one-half inches. 
It is found on the bottom in clear small brooks, where it lies partly concealed by 
sand, and changes its colors according to its surroundings. The body is slender, 
spindle-shaped. The conical head is contained slightly more than four times 
