LAMPREYS 4.ND FISHES OF INDIANA. 233 



Family PERCOPSID.E. 



Body elongated ; covered with strongly ctenoid scales. Head naked ; 

 the bones cavernous. Dorsal and anal short. An adipose fin present. 

 Teeth on the premaxillaries and lower jaw; none on vomers and pala- 

 tines. Branchiostegals six. Premaxillaries forming the upper mar- 

 gins of the mouth. Pseudobranchiie large. 



Genus PERCOPSIS Agassiz. 



Dorsal originating immediately behind the veutrals. No supplemen- 

 tary bone. Gill-rakers short. A medium bony crest along the middle 

 of the head. 



Percopsis guttatus Agassiz. 



Trout perch. 



Jordan and Gilbert, 1 882, <V, 322. 



Body elongated and compressed. Depth in the length iour and one- 

 half to five times. Head pointed and compressed ; the profile increasing 

 in convexity as it uears the snout. Mouth horizontal, small, the maxil- 

 lary not reaching the eye. The bone of the head with cavities for mucous 

 glands. Dorsal rays ten or eleven ; anal rays eight. Scales strongly 

 ctenoid ; 8-55-8. Color pale olivaceous, with numerous splotches of 

 brown. Sides with a silvery lateral band, especially distinct behind. 

 Belly white. Length about six inches. 



Occurs from the Potomac River to Kansas, and from the Ohio Kiver 

 to the Great Lakes It appears to be quite abundant in Lake Michigan, 

 and Dr. Jordan {10, '74, 220) records it from Jefiersouville, on the Ohio 

 River. It is to be expected in any of the larger streams of Indiana. In 

 the Great Lakes, it is found from shore to a depth of twenty fathoms. 

 It is taken with hook and line from the piers at Chicago, and is sometimes 

 washed up on the beach. While most closely related to the Salmonidre, 

 this fish has some characters in common with the perches. 



Order 8 HAPLOMI 



This order differs essentially from the Isospondyli in having no pre- 

 coracoid arch. For combinations of characters by means of which the 

 two orders may be distinguished, the student is again referred to page 170. 



Families of HAPLOMI. 



'i^ Upper margin of mouth formed wholly by premaxillaries. 



t Mouth large; lower jaw projecting; gill-membranes connected 



with the isthmus ; head scaleless. Ambhjopsida', p. 234. 



ft Mouth small ; jaws equal ; gill membranes free from the 



isthmus; head scaled. Cyprinodontidn', }:> 235. 



