20 EEPOET OF COMMISSIONER OF FISH AND FISHERIES. 



indicated by the " distance from snout to nape," varies from .19 to .23. 

 The length of snout, measured from a line drawn perpendicularly 

 through the centre of the orbit, varies from .09 to .11. The length of 

 maxillary varies from .12 to .14i ; that of mandible from .15 to .18. The 

 diameter of the eye enters 4J times in the length of the head ; its width 

 varies from .11 to .15 in very fat individuals. 



Shape of hodij. — This is exceedingly variable, and the variation is 

 caused largely by the fatness of the individual. In very plump ones, 

 the expansion of the belly throws back the origin of the ventrals and 

 anal, and greatly changes the appearance of the fish. In the specimens 

 before me the height of the body ranges from .31 to .38^. The table of 

 measurements subjoined shows the effect of increased height of body 

 upon the other measurements of proportion. 



Fins. — The range of variation in the position of the dorsal is indicated 

 in the diagnosis. There is no appreciable correlation between the 

 positions of the dorsal and anal in the same specimen. The insertion of 

 the anal is distant from the snout from .08 to .75. The length of the rays 

 in dorsal, anal, ventral, and caudal vary much, as the table of measure- 

 ments indicates. In the caudal the upper lobes vary from .16 to .25, the 

 lower lobes from .18 to .27. The relation of the pectoral and ventral fins 

 is much affected by the length of the head, the insertion of the former 

 being thrown much farther back in long-headed individuals. 



Scales. — The degree of serration varies much in individuals as well as 

 the squamation of the bases of the vertical fins, and the number and 

 regularity of the body-scales. In young individuals the scales are ar- 

 ranged with much regularity, but in the adults I have strong reason to 

 believe that other scales are intercalated here and there throwing the 

 arrangement into great disorder and rendering an accurate enumeration 

 impossible. ^ 



Subspecies. 



The series before me embraces some two hundred specimens of Bre- 

 voortia tyrannus of various ages, seasons, and localities. Almost every 

 feature is subject to wide variations, and there is usually no decided 

 correlation between different characters except that a long head is accom- 

 panied by long jaws and a pectoral set farther back and extending 

 more nearly to the insertion of the ventral. There are, however, certain 

 groups of individuals which can be included within a diagnosis, which 

 may serv^e to distinguish them from all the others of the same species. 

 To what extent it is desirable to define varieties which are not separated 

 geographically, I am not well satisfied. The exact meaning of the terms 

 "sub-species" and "variety," as employed by Cope, Coues, Gill, Yarrow, 

 and other recent writers, has not been definitely interpreted. It seems 

 desirable, however, to designate in some way the limits of variation 

 from the normal specific types in different directions. With this pur- 

 pose, and remarking that by a subspecies I mean simply a divergent form 

 connected by intermediate forms with the typical specific form, I have 



