CRITICAL NOTES ON MYLOCHEILUS LATERALIS AND LEUCISCUS 



CAURINUS. 



By John Otterbein Snyder, 

 Assistant Professor of Zoology, Leland Stanford Junior Unlversitij. 



Girard'', in 1850, placed Leuciscus caurlnus Richardson* in the ^enus 

 Mylocheilus along with 2f. lateralis Agassiz & Pickering^ and 3L 

 fraterculus^ which he described from Monterey, Cal. Mylocheilus has 

 not been found in California by recent collectors, nor is there any 

 stream near Monterey containing fresh-water fishes. The specimens 

 alleged to have been taken there were probably from the north, and 

 M. fraterculus has long been identified, no doubt correctly, with the 

 form found in the Columbia River. 



Recent authors have not only continued to associate M. lateralis 

 with L. cauriiius, but they have also considered the species identical, 

 a proceeding wholly at variance with the facts. Richardson described 

 a form closely resembling Ptychocheilus oregonensis^ with which he 

 sa3's it was confused by the collector. He also observes '^ that P. 

 oregonensis is so similar in general appearance to this species that it 

 may readily be confounded with it. However, a comparison of the 

 original descriptions of M. lateralis and L. caurinus will leave no 

 doubt as to the distinctness of these two forms. Aside from the phar- 

 yngeal teeth, which Richardson does not mention, his species differs 

 from M. lateralis in the absence of a maxillary barbel % in having 10 

 dorsal and 9 anal rays, a longer snout and larger mouth, scales sub- 

 orbicular in shape, and other less conspicuous characteristics. The 

 Mylocheilus caurinus of recent authors is synonymous with M. lateralis 

 Agassiz & Pickering. 



While conducting explorations in Oregon under the direction of the 

 United States Bureau of Fisheries the writer secured a specimen from 

 the Willamette River, near Corvallis, which agrees almost perfectly 



aGirard, Charles, Proe. Ac. Nat. Sci. Phila., 1856, 169. Girard probably had specimens of ilf. 

 lateralis which, on account of some slight individual variations, he identified as L. caurinus. He 

 certainly did not have examples of the latter species as it is M'ithout barbels. 



& Richardson, John, Fauna Boreali- Americana, III, 304, 1836. 



c Agassiz, L., Am. Jour. Sci. Arts, XIX, 1855, 281. 



d Richardson, op. cit., p. 305. 



eRichardson, op. cit., p. 120. "The Lcucisci, or Daces, have a short dorsal and anal, are destitute 

 of spinous rays or barbels, and exhibit nothing peculiar in the structure of their lips." 



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