MILNER FISHERIES OF THE GREAT LAKES. 71 



shields, like a small button, iu a few mature specimens. The keels 

 of the dorsal shields have been seen in a few individuals slightly promi- 

 nent, where they had attained the length of about three feet, though 

 these might not have been older than some of a smaller size who had 

 not had so rapid a growth. 



(24f7.) Description of adult specimen. — Head from orbit to pectoral 

 arch. .20 of length of trunk; an oblique line from orl)it to posterior 

 of supra-occipital plate, .19 of length of trunk. 



The following proportions are given in one-huudredths of the distance 

 from the orbit to the posterior edge of opercular opening, measured in 

 a line with the axis of the body: Width of head at anterior nasal ori- 

 fices, .34 ; width of head at orbits, .50 ; width of head at temporal 

 plates, .01^; width of head at narrowest part of opercular openings, 



P. 40 ; D. 35 ; A. 2G ; C. f f 



Dorsal shields, 4 anterior ones apparent; lateral shields, 38, reduced 

 to indistinct, narrow remnants ; ventral shields, no trace remaining j 

 shields separated and without keels. 



Length, 5 feet 7 inches. 



Locality, Ecorse, Mich., Detroit Eiver. 



(24e.) Description of young specimen. — A comparison of young speci- 

 mens with mature ones shows the greatest differences to be the develop- 

 ment of the shields, and the very much longer snout. The number of fin- 

 rays, the series of shields, and the form and arrangement of the bones of 

 the head, on all but the rostrum, correspond to the older specimens. 



Head from orbit to pectoral arch, .17 of length of trunk; an ol)lique line 

 from orbit to posterior of suju-a-occipital plate .IGi of length of trunk. 



The proportions of the head are given in one-hundreths of the distance 

 of the orbit to the pectoral arch. Width of head at anterior nasal ori- 

 fices, .40; width of head at orbits, .50; width of head at temporals, .70; 

 width of head at narrowest point of opercular openings, .G6i|. 



P. 37;D.37; A. 24;C. f£. 



Dorsal shields, 11; lateral shields, 34; ventral shields, 8 and 9; keels 

 slightly worn. 



Length, 28.2 inches. 



Locality, Bayfield, Wis., Lake Superior. 



Specimens from Lakes Erie, Huron, Michigan, and Superior have no 

 more variation in charactejrs than can be found among the specimens 

 taken at a single fishing ground. 



(24/.) Size of mature fish. — The sturgeon of this species attains the 

 largest size of any fish of the lakes. They are taken only within com- 

 paratively shoal waters, and in some of the bays, and among the islands 

 they are very abundant. 



The largest specimen it has been my fortune to see did not quite 

 attain the length of six feet, though there are traditions in localities ou 



