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THE BONY FISHES AND GANOIDS 



Allied 



Families 



Of the three remaining and comparatively unimportant families, 

 included in the perch-like section of the spiny-finned fishes, it is only 

 possible to make very brief mention. The first of these, the Nandidce, 

 differs from all the foregoing by the incompleteness or absence of the lateral line; 

 the dentition, although feebly developed, being more or less complete, and the 

 preopercular bone having no connection with the orbit. The oblong and oval body 

 is scaled; the number of spines in the dorsal fin is nearly equal to that of the rays; 

 the three-spined anal has its soft portion similar to the soft dorsal; and the thoracic 

 pelvic fins have one spine and four or five rays. The small Oriental fresh-water 

 fishes known as Nandus, Badis, etc. , constitute a group of the family characterized 

 by the presence of five rays in the pelvic fins, and the absence of false gills. They 

 are common in all parts of India, some preferring ditches and inundated rice fields, 

 while others frequent clear streams. All are carnivorous, and the largest does not 



B^EEKER'S PLESIOPS. 

 (One-half natural size.) 



exceed seven inches in length. The second group, as represented by Plesiops from 

 the Indo-Pacific coral reefs, and Trachinops from the Australian seas, although also 

 including only small forms, are, on the other hand, marine; and are characterized 

 by having only four rays to the pelvic fins, and by the presence of false gills. 

 In Plesiops the lower rays of the pelvic fins are elongated and split at the ends; the 

 soft dorsal and anal fins being likewise of considerable length. The figured 

 species (P. bleekeri), which attains a length of ten inches, is from the coral islands 

 of the Southwest Pacific; it has the lateral line broken. 



The second family (Polycentridez) is represented only by the genera 

 Polycentrus n , 



rolycentrus and Monoctrrhus, from the rivers on the Atlantic side or 



tropical America; our illustration showing a member of the former genus (P. schom- 

 burgki). These fishes are characterized by the absence of a lateral line, and the 

 great number of spines in both the dorsal and anal fins. The thoracic pelvic fins 



