GREAT LAKES COREGONIDS 



403 



Reighardi differs from hoyi in having the lower jaw shorter while in hoyi it is 

 usually equal to or longer than the upper; in having fewer gill rakers on the first 

 branchial arch and shorter paired fins, as will appear from the comparisons: 



Gill rakers on the first branchial arch : 



reighardi, (30) 34-38 (43) , with 3 per cent more than 40. 



hoyi, (37) 41-44 (48), with 86 per cent more than 40. 

 Pv/P: 



reighardi, (1.7) 2-2.5 (2.8), with 83 per cent more than 2. 

 hoyi, (1.6) 1.8-2 (2.3), with 21 per cent more than 2. 

 Av/V: 



reighardi, (1.2) 1.4-1.7 (1.9), with 91 per cent more than 1.3. 

 hoyi, (1.1) 1.3-1.5 (1.7), with 60 per cent more than 1.3. 



In addition, reighardi has, on the average, a proportionately shorter head and 

 maxillary and more lateral-line scales. Reighardi spawns in May or June and hoyi 

 in March, so that at times the state of development of the sex organs also may be 

 of aid in separating the species. 



Reighardi is distinguishable from artedi by the fewer gill rakers on the first branchial 

 arch, which seldom are more than 41 in the former and not less than 41 in the latter, 

 and a less triangular head, as seen from the side. The snout of reighardi is sharply 

 truncated in front by the nearly vertical position of the premaxillaries. Reighardi 

 has, on the average, shorter pectorals, a somewhat longer maxillary, the mandible 

 is more conspicuously tipped with black, and the back is usually paler in color. 

 Reighardi spawns in the spring and artedi in the fall, so that the state of development 

 of the sex organs may serve as a differentiating character at times. 



GEOGRAPHICAL DISTRIBUTION 



Table 32 shows my data on the occurrence of reighardi in Lake Michigan. They 

 are shown platted on a chart of the lake in Figure 4. There are 43 records, all but 

 14 of them made from the commercial chub nets. While the species seldom has been 

 found in numbers, a few individuals have been present in most lifts examined, even in 

 that one made on the Sheboygan reef (record 8) ; and it may be stated safely that the 

 species is distributed along the shores of the lake and probably on some of the reefs. 



BATHYMETRIC DISTRIBUTION 



Data on the depth range of reighardi have been collected principally from an 

 examination of the lifts of the to 2% inch chub nets set at depths of 12 to 90 fath- 

 oms. All the chub lifts examined have yielded at least a few examples of this species, 

 except those made off Milwaukee, Wis., on September 24, 1920, 9 miles NNE. in 

 22 to 25 fathoms and on November 15, 1920, 20 miles ESE. in 28 to 35 fathoms, and 

 that made on November 19, 1920, 10 miles northwest of Michigan City, Ind., in 

 18 fathoms. The two last were made on the spawning grounds of zenithicus, and 

 it is not surprising that no reighardi occurred there, while the former was made on 

 grounds unfrequented by chubs of any species. In Green Bay, where 2% to 2% 

 inch nets are set for herring, reighardi was seen only in those nets set in the deepest 

 water. A few individuals were taken in a gang of nets on August 18, 1920, off Boyer 

 Bluff, Washington Island, Wis., in 18 to 24 fathoms (record 1). 



In the catches of the l^-inch bait nets examined from seven ports (see p. 354) 

 small reighardi were found always. Lifts were examined from depths of 26 to 40 



