Standard length | (053-063) | (072-078) | (095-104) | | | Gill rakers | 30 | 17 | 9 (1st arch) | (29-31) | (16-18) | (8-10) | | | Number scales in | 54 | 54 | 56 lateral line | (53-55) | (54-55) | (52-64) | | | Predorsal scale-rows | 25 | 27 | 35 | (23-27) | (27-28) | (34-36) | | | Anal rays | 7 | 7.3 | 8 | (6-7) | (7-8) | 8 | | | Vertebrae | 40 | 42-44[A] | 42-43 ---------------------+-----------------+---------------+----------------- [A] Three deformed vertebrae in one specimen with 44; other two specimens have 42 vertebrae. The hybrids seem uniformly intermediate between the parental species. Application of the hybrid index to the characters listed in Table 3 results in a value of 55.7 when _C. a. plumbeum_ is assigned the value 0. The pharyngeal arches of the hybrids are peculiarly deformed. Expressed in terms of the one-or two-rowed arrangement common to all North American cyprinids, tooth-counts of 0,5-4,1; 1,3(?)-4,0; and 2,5-4,1 best fit the three fish. However, one arch bears only three teeth, all deformed and badly aligned, plus a pit that presumably represents a lost fourth tooth. At the other extreme, one arch bears eight teeth, some of which are attached to the arch between and behind others that are countable as part of the basic main row. Supernumerary teeth and other deformities may have resulted from abnormalities in the replacement process. In some cases, replacement teeth probably failed to develop; in others, replacement teeth seemingly developed, but attached to the arch in abnormal positions, with or without loss of previous teeth, causing irregularity in alignment. Hubbs (1951) described an irregular (seemingly three-rowed) alignment in a fish that Hay (1888:249) reported from western Kansas as _Squalius elongatus_. However, Hubbs considered the specimen to be an aberrant example of _S. atromaculatus_, and the characteristics that he lists for it do not correspond closely with those of the hybrid specimens that we have. Evans and Deubler (1955:32) found three rows of teeth in two of 150 specimens of _Semotilus_, and attributed the abnormality to failure of old teeth to fall out after formation of new teeth. The teeth of _Campostoma_ usually number 0,4-4,0, and those of _Semotilus_ 2,5-4,2. The pharyngeal arches are much smaller in _Campostoma_ than in _Semotilus_.