340 



BULLETIN OF THE BUREAU OF FISHERIES 



DESCRIPTIONS OF THE COREGONIDjE IN THE GREAT LAKES 



Genus LEUCICHTHYS Dybowski 



Argyrosomus Agassiz, 1850, p. 339 (clupeiformis of DeKay, not of MitchiH-artedi) . Not of de la 

 Pylaie. 



Leucichthys Dybowski, 1874, p. 390; Dybowski, 1876, p. 18 (Coregonus omul Pallas). 

 Allosomus Jordan, 1878, p. 361 (Coregonus tullibee Richardson). 

 Thrissomimus Gill, in Jordan and Evermann, 1911 (Coregonus artedi LeSueur). 

 Cisco Jordan and Evermann, 1911 (Argyrosomus nigripinnis Gill). 



Dybowski (1874) proposed the name Leucichthys for Coregonus omul Pallas and 

 Coregonus tugun Pallas, coregonids with "der Mund vorderstandig oder halb ober- 

 standig. Die Symphyse des Unterkiefers mit einer hockerartigen Anschwellung." 

 There is nothing in the descriptions of either omul or tugun to indicate that they 

 differ from our lake herrings, except that he says for tugun "Oberkiefer mit einer 

 Reihe schwacher Zahnchen besetzt." It is apparent at once that no fish held to be 

 a Coregonus would likely have toothed maxillaries, and reference to the original 

 paper, which Dybowski (1874, p. 383) says was presented for publication to the 

 Siberian division of the Geographic Society in Irkutsk in the winter of 1871, but 

 which did not, in fact, appear in the publications of the society until February, 

 1876, suggests that Dybowski meant "Unterkiefer" instead of "Oberkiefer." The 

 Russian edition says of tugun "mandible provided with a row of faint teeth." Dy- 

 bowski, in his original paper, rated Leucichthys as a subgenus together with Core- 

 gonus sensu strictiore under the genus Coregonus. European ichthyologists generally 

 have not recognized Leucichthys as a genus or even as a subgenus. 



Jordan and Evermann (1911) substituted the name Leucichthys for the genus 

 Argyrosomus established by Agassiz to include the lake herrings, but which (the 

 authors quote Gill here) was preoccupied, the name having been used in 1835 by de 

 la Pylaie for the "maigre" (aquila) of the Mediterranean. Under Leucichthys 

 three subgenera — Allosomus, Thrissomimus, and Cisco — are recognized. The rep- 

 resentatives of the subgenus Allosomus I regard as subspecies of certain species in 

 the Thrissomimus group. I find, further, no possibility of distinguishing struc- 

 turally between the species of the latter group and those of Cisco and therefore do 

 not subdivide the genus Leucichthys. 



The Great Lakes representatives of the genus Leucichthys are fish of medium 

 size, seldom larger than 1 Yi pounds in weight. The premaxillaries are longer than 

 wide and oblique or nearly vertical but never retrorse in position. There are two 

 flaps between the openings of each nostril. The exposed area of the scales of the 

 lateral line is not conspicuously smaller than that of those of the adjacent rows. 

 The gill rakers are relatively long and numerous (johannx excepted). The maxillary 

 usually is contained less than 3 times in the head. The mandible is contained not 

 more than 2.3 times in the head. Vestigial teeth usually are present on the pre- 

 maxillaries, palatines, mandible, and tongue. The prefrontal bone is elongated and 

 extends almost completely over the orbit. The carina of the frontals extends to 

 the frontal-parietal suture. 



The species described in the following pages fall into three ecological groups 

 whose relations are considered in another place. These groups are, in the order in 

 which they are considered in the text, (1) the chubs johannse, alpense, zeniihicus, 



