30 



Fig.9: Ventral profile of heads of ( A) Couesius plumbeus (KU 18965, 73.5 mm SL) and (B) Phoxi- 

 nus erythrogaster (KU 10629, 62.5 mm SL), showing the preoperculomandibular canal (in black). 

 Scale bars = 1 mm. 



preopercular canal in Phoxinus is much shorter than that in other genera in the Chub clade. 

 In other genera of the Chub clade (e.g., Nocomis), the canal ends near the tip of the as- 

 cending limb of the preopercle (Coburn & Cavender 1992). In Phoxinus, however, the 

 canal terminates at the middle of the preopercle. - TS 6: Preopercular sensory canal ter- 

 minates at or close to the tip [0], or at about the middle [1] of the ascending limb of the 

 preopercle bone. 



7. Preoperculomandibular canal (Fig.9A-B). In Phoxinus, the preoperculomandibular ca- 

 nal is interrupted between the posterior end of the mandibular portion and the anterior end 

 of preopercular portion, thus the mandibular and the preopercular canals are formed 

 (Fig.9B). This condition is not found in other genera of the ingroup or in the outgroups 

 (Fig.9A). - TS 7: Preoperculomandibular canal continuous [0], or interrupted into two 

 portions [1] between the mandibular and the preopercular bones. 



8. Basal radii of scales (Fig.lOA-C). Generally, scales of most cyprinids bear apical (po- 

 sterior) radii only (Chu 1935) (Fig.lOA). In the exoglossins of the Chub clade, no genus 

 bears basal radii on the scales. Coburn & Cavender (1992) indicated that Campostoma or- 

 natum bears basal (anterior) radii on the scale. However, no basal radii were found on the 

 scales in the specimens of C. ornatum and C. anomalum I studied. In the Hemitremian 

 clade, Coburn & Cavender (1992:352) mentioned the basal radii occurring within the Chub 

 clade only in Rhynchocypris and Phoxinus of the taxa examined. However, my studies 

 show that four genera in the Hemitremian clade, i.e., Rhynchocypris, Lagowskiella, Eu- 

 pallasella, and Phoxinus, bear both basal and apical radii on their scales (Fig. 10C). Ba- 

 sal radii are absent on the scales of Semotilus, Couesius, Hemitremia, and Margariscus of 

 Hemitremians (Fig.lOB). Tribolodon does not have basal radii (Chu 1935, Coburn & Ca- 

 vander 1992). 



