546 



BULLETIN OF THE BUREAU OF FISHERIES 



above the lateral line, with a sprinkling of dots down to about the fifth row below. 

 The top of the head and the preorbital area are heavily sprinkled with fine dots, 

 which often collect to form small spots, particularly in the occipital region. Pigment 

 is present on the oculars and on the operculum. The cranial border of the dorsal, 

 the tips of its rays, and the rim of the caudal are washed with smoky. The other 

 fins are usually immaculate, though there are occasionally a few pigment dots on the 

 pectorals and ventrals, particularly on their inner surface. 



Pearl organs have been seen on no individuals of the species. Only one adult 

 specimen was taken in the breeding season, and in the case of this specimen (collected 

 on November 19, 1920, out of Michigan City) the epidermal excrescences may have 

 been eliminated by rough treatment subsequent to its capture. It is probable that 

 the development of pearls in the species of Lake Michigan is not different from that 

 in the Lake Huron form. 



VAKIATIONS 



Racial variations. — There are no data available for a discussion of local variations. 



Size variations. — An examination of 42 specimens ranging in length between 

 156 and 210 millimeters, taken in Platte Bay on the Michigan shore, indicates that 

 small individuals have a larger head and eye and somewhat longer paired fins. A 

 comparison of these values for the two classes of specimens follows: 



L/H: 



Large fish, (4.9) 5.2-5.4 (5.6). 

 Small fish, (4.7) 5-5.1 (5.2). 

 H/E: 



Large fish, (4.1) 4.3-4.6 (5). 

 Small fish, (3.5) 3.7-3.9 (4). 



Pv/P: 



Large fish, (1.8) 1.9-2.2 (2.3). 

 Small fish, (1.8) 1.9-2 (2.1). 

 Av/V: 



Large fish, 2.1-2.3 (2.5). 

 Small fish, (1.8) 2-2.2 (2.5). 



The body depth, of course, is also less, proportionally, in small specimens. 



Small individuals in the collection (all those under 200 millimeters and often 

 those up to 230 millimeters) show parr marks. These marks are distinct, roundish, 

 dusky spots 2 to 4 millimeters in diameter, irregularly spaced, separated 2 to 8 milli- 

 meters from one another, and scattered more or less at random over the dorsolateral 

 and dorsal surfaces, though there is often an appearance of arrangement in sinuous 

 rows. They are most conspicuous and most numerous on the second to fifth rows 

 of scales above the lateral line and disappear last in this region as the individual grows. 

 Frequently there are dots along the lateral line, also, which are larger and fewer in 

 number than on the rows above it; and there are also fainter marks on the dorsal 

 surface, particularly in the predorsal area. Dymond (1926, PI. VIII, fig. 1) shows a 

 specimen with these parr marks. 



It is noteworthy that of 17 collected specimens between the length of 220 and 

 300 millimeters, only 4 are sexually mature. They are divided as follows, according 

 to size and sex: Mature — 255 female, 267 male, 279 female, and 295 male; immature — 

 220 male, 220 male, 221 male, 226 female, 232 female, 239 male, 242 female, 249 

 female, 254 female, 256 female, 269 male, 270 female, and 293 female. 



The maximum size reported for the lake is about 4 pounds. 



