GREAT LAKES COREGONIDS 



447 



Lateral-line scales: 



kiyi, (71) 76-87 (91), with 89 per cent more than 76. 



hoyi, (63) 68-76 (81), with 8 per cent more than 76. 

 H/E: 



Myi, (3.6) 3.9-4.2 (4.4), with 7 per cent more than 4.2. 

 hoyi, (3.7) 4-4.5 (4.7), with 39 per cent more than 3.7. 

 H/ad: 



kiyi, (2.7) 3.2-3.7 (4.1), with 15 per cent more than 3.7. 

 hoyi, (3.2) 3.6-4.3 (5), with 72 per cent more than 3.7. 

 Scale rows in front of dorsal and ventrals: 



kiyi, (40) 41-44 (47), with 79 per cent more than 41. 

 hoyi, (37) 40-41 (46), with 25 per cent more than 41. 



The ventrals are also somewhat longer, relative to the distance from their 

 insertion to that of the anal (Av/V), in Tciyi. As Tciyi spawns in August and hoyi 

 in November or later, the state of development of the sex organs will often be serv- 

 iceable also in separating individuals of the two species. 



As only one specimen of prognathus is known to exist in collections, it is not 

 possible to give criteria for distinguishing the two forms, but there are decided 

 differences between the two in respect to absolute size attained and the time of 

 spawning. The largest collected Tciyi measures only 263 millimeters, and nets of 

 23^-inch mesh are required for the capture of the species, while prognathus was 

 commonly larger than 300 millimeters and was taken only in nets of 3-inch or larger 

 mesh. The species differed, also, in time of spawning. Kiyi spawns in August, 

 while prognathus is said to have spawned in January. 



Usually Tciyi can be distinguished at once from artedi by the more ovate body 

 outline, as seen from the side, as in the former the predorsal contour is strongly 

 arched. In addition, Tciyi has fewer gill rakers on the first branchial arch, a larger 

 head and eye, a longer mandible, and paired fins. These characters are compared 

 below for the two species: 

 Gill rakers on the first branchial arch: 



kiyi, (41) 43-46 (48), with 15 per cent more than 46. 



artedi, (41) 46-50 (54), with 67 per cent more than 46. 

 L/H: 



kiyi, (3.8) 4.1-4.2 (4.4), with 5 per cent more than 4.3. 

 artedi, (3.7) 4.3-4.7 (4.9), with 74 per cent more than 4.3. 

 H/E: 



kiyi, (3.6) 3.9-4.2 (4.4), with 7 per cent more than 4.2. 

 artedi, (3.9) 4.1-4.4 (4.9), with 56 per cent more than 4.2. 

 Pv/P: 



kiyi, (1.5) 1.7-2 (2.2), with 11 per cent more than 2. 

 artedi, (1.7) 1.9-2.1 (2.5), with 38 per cent more than 2. 

 Av/V: 



kiyi, (1) 1.2-1.4 (1.6), with 7 per cent more than 1.4. 

 artedi, (1.3) 1.5-1.8 (2), with 94 per cent more than 1.4. 

 Mandible compared with upper jaw: 



kiyi, shorter, 2 equal, 30 longer, 98 or 75 per cent longer. 

 artedi, shorter, 130 equal 121 longer, 77 or 23 per cent longer. 



Kiyi spawns in August and artedi spawns in late November, so that the state 

 of development of the sex organs, particularly of females, also is a valuable character 

 for separating the two species. 



A discussion of the distinctions between Tciyi and reighardi is given on page 414. 



