12 AMERICAN FISHES. 



certain areas within the limits of its range. The British Isles, France, 

 the Rhine valley and Switzerland, New England and the South Atlantic 

 states, are without it, and its distribution in Asiatic Russia is more restricted 

 than that of Perca. 



This form is more subject to variation than the Perch, and probably a 

 more recent product of evolution, and it has become differentiated into seve- 

 ral fairly well-marked types. 



The North American species may be divided into two groups: (i) the 

 typical form, most closely related to those of Europe, and (2) the form 

 with small eyes, slender body, pointed head, smaller second dorsal and 

 with pyloric cceca set aside by Gill and Jordan in the subgenus Cynoperca. 



In the latter category is placed S. canadense, having its spinous dorsal fin 

 ornamented with two or three rows of round black spots, and without a blotch 

 posteriorly, but with a dark patch at the base of each pectoral : within 

 the limits of this species, Jordan recognizes three varieties or subspecies 

 which intergrade to some extent, but which by old-school naturalists would 

 have been regarded as valid species. The first of these is the Sanger or 

 Pickering of the St. Lawrence region, .S". canadense canadense, with 

 the opercles and bones of the head considerably rougher, the number or 

 opercular spines, (which are merely the free ends of the strire), increased, 

 and the head more closely and extensively scaly. 



The second is the common Sand Pike, or Sauger, of the Great 

 Lakes, S. canadense griseum, the Lucioperca grisea of DeKay's " New York 

 Fauna," and many other ichthyologies. This form is now plentiful in the 

 Ohio River into which it is supposed to have made its way since the con- 

 struction of the Ohio and Erie Canal. 



The third is the Sand Pike of the upper Missouri, S. canadense borcum . 

 which is rather slenderer than that of the Great Lakes, having a long 

 slender nose and a head more flattened and snake-like. 



A certain type of coloration is characteristic of S. canadense in all its 

 forms, and it has fewer rays in the second dorsal fin, there being only 18, 

 more scaly cheeks, a more prominent armature of the operculum and most 

 significant of all, the pyloric coeca are small and unequal in length and 

 are never less than four in number, and sometimes as many as seven. In the 

 other American species these number only three, and are nearly equal in 

 length and about as long as the stomach. Whoever wishes to identify our 

 Pike-Perches accurately must not fail to dissect them and examine this fea- 

 ture of internal structure. 



