230 



LOWER VERTEBRATES. 



Fig. 130. — Etheostoma lineolataj striped 

 darter. 



We can only pause to mention several species which may give an idea of the range 

 of variation in the family. 



The Etheostoma lineolata, or striped darter, is a typical form of the group ; as 

 the name indicates, it has lines of color along the longitudinal rows of scales. It has 

 been said to be " one of the most singular and handsome of the darters." It inhabits 

 the streams of the west, from Indiana to Minnesota. 



The 3Iicroperca pimctulata, or least^darter, is noteworthy as being the smallest 



species of this group of small fishes. It abounds in 

 the clear streams of the northwestern States, and only 

 srrows to a length of an inch and a half. 



The Animocrypta pellucida, or sand-darter, is an 

 Ohio valley fish. It and its immediate relatives differ 

 from most of the family in preferring " a sandy bottom, 

 where, by a sudden jilunge, the fish buries itself in the sand and remains quiescent for 

 hours at a time, with only its eyes and snout visible." 



Another family of special interest to the American naturalist is known as Cen- 

 TEAECHiD^. It is to this that the species called sun-fish, rock-bass, and black-bass 

 belong. They are all inhabitants of the fresh water, and most of them have a pecu- 

 liar form by which they may be readily distinguished from at least all other American 

 fresh-water fishes. The body is compressed and oval, balanced ^o that there is no 

 greater projection upwards than downwards, except perhaps at the front of the back. 

 The lateral line is continuous and concurrent with the back. The head is of moderate 

 size ; the nostrils are normally double ; the cheeks and opercula are scaly ; and the 

 operculum generally ends in a rounded flap, but sometimes, though rarely, in a 

 spinous one, as in the black-bass ; in any case there is a black spot on the posterior 

 extension of the operculum, and the extension is often such as to remind one of an ear ; 

 often the black is bordered by red or yellow, and then it presents a very striking 

 appearance. The dorsal fin is long, and generally there are ten spines and ten rays ; 

 rarely, as in the black bass, there are twelve or thirteen rays, and in one type the 

 spines are reduced to six or eight. The anal fin is just opposite and like the soft 

 part of the dorsal fin, or, sometimes, obliquely placed and nearly as large as the entire 

 dorsal fin. There are some interesting features in their habits. All the species con- 

 sort together in pairs during the breeding season, and are very domestic; they clean 

 a circular spot of ground near the shore, where the female lays her eggs, and male and 



female guard this nest with care, and cour- 

 ageously drive off intruders. Nearly fifty 

 species of the family are known, which are 

 distributed among ten genera. 



The black-basses are the least specialized 

 type of the family, and represent the genus 

 called by American ichthyologists Micropterus, and by Europeans — at least for- 

 merly — ■ Grystes and Huro. This genus is distingui?;hed by the comparatively 

 elongate form of the body, the low dorsal, and especially the slight development of 

 the spines, which decrease to the soft portion, leaving a considerable emargination 

 between the bulk of the spinous and the soft portions. The operculum has a spini- 

 forra projection ; the mouth is large, and the caudal emarginated. Two species of 

 this genus are generally recognized, the large-mouthed black-bass {M. salmoides) and 

 the small-mouthed species {M. dolomieu). These resemble each other very much, and 



^S ^^^ ^^% 



Fig. 131. — Ammocrypta pelliieida, sand-darter. 



