28 



2. Posterior barbel (Fig.4A-B). The posterior barbel of Couesius is a papillate appendage 

 derived from the upper rictal tissue which is not homologous with the barbels of other 

 "barbeled cyprinids ,? (i.e.. cyprinins) (Howes 1985). This posterior barbel is located at the 

 corner of the mouth, and present in Couesius only (Fig.4A). - TS 2: A posterior barbel 

 absent [0], or present [1]. 



3. Primary lamellae of the olfactory organ (Fig.5A-B). The primary lamellae of the ol- 

 factory organ are arranged at both sides (lateral and medial) of the axis in the olfactory 



Fig. 7: Supratemporal and otic canals (in black), frontal, pterotic. parietal, epioccipital. and supraoc- 

 cipital bones in hemitremians and in the outgroup. A: Nocomis platyrhynchus (KU 18926. 46.5 mm 

 SL); B: Semotilus corporalis (KU 18856, 58.0 mm SL): C: Couesius plumbeus (KU 18881, 56.6 mm 

 SL). Scale bars = 1 mm. 



