113 



Fig. 71: Lateral view of the opercular series of Phoxinus. A: P. tennesseensis (UT 44.5274, 50.0 mm 

 SL); B: P. phoxinus (KU 22856, 56.0 mm SL); C: P. cumberlandensis (KU 18934, SL 54.3 mm SL); 

 D: P. eos (KU 12255, 43.0 mm SL); E: P. issykkulensis (P- 10696, 42.4 mm SL); F: P. oreas (KU 

 3259, 52.2 mm SL). Scale bars = 1 mm. 



Interopercle (Figs.71A-F). The interopercle is placed at the anteroventral portion of the 

 opercular series. It is partially overlapped by ventral side of the preopercle dorsally, and 

 by anterior portion of the subopercle posteriorly. 



The interopercle is elongated triangular plate-like and tapes anteriorly; therefore, its ante- 

 rior portion is narrower than its posterior portion. The shape of its posterior margin va- 

 ries individually. The posterior margin can be concave, slope, or round in different 

 specimens of a single species. 



Preopercle (Fig.71A-F). The preopercle is a "L"-shaped bone and located anteriorly to 

 the opercle. Its posterior portion contacts the anterior margin of the opercle, its ventral 

 margin contacts with dorsal side of the interopercle. It is crescent in shape, and its middle 

 portion is broader than its anterior and dorsal portions. No variation with phylogenetic 

 significance is observed in Phoxinus. 



Subopercle (Fig.71A-F). Placed ventrally to the opercle, the subopercle contacts the 

 opercle dorsally and the preopercle anteriorly. 



