CRITICAL NOTES ON MYLOCHEILUS LATERALIS AND LEUCISCUS 



CAURINUS. 



By John Otterbein Snyder, 

 Assistant Professor of Zoologij, Leland Stanford Junior University. 



Girai'd'', in 1S5(), placed Leuciscus caurlnus Richardson* in the ^enus 

 Mylocheilus along with J/i lateralis Agassiz & Piclcering^ and M. 

 fraterculus^ which he described from Monterey, Cal. Myloclieilus 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 If. lateralis 

 with L. caurlnus., 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 

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

 (yregonensis 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. caurlnus 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 ra3^s, a longer snout and larger mouth, scales sub- 

 orbicular in shape, and other less conspicuous characteristics. The 

 Mylocheilus caurimis 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, Proc. Ac. Nat. Sci. Phila., 1856, 169. Girard probably had specimens of M. 

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

 certainly did not have examples of the latter species as it is without barbels. 



'> Richardson, John, Fauna Boreali- Americana, III, 304, 1836. 



c Agassiz, L., Am. Jour. Sci. Arts, XIX, 1855, 231. 



rf Richardson, op. cit., p. 305. 



e Richardson, op. cit., p. 120. "The Lcuciscl, or Daces, have a short dor.sal and anal, are destitute 

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



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