104 Mr. C T. Regan on the African 



anteriorly. Vertebraj 29-32 (15-10+ 14-lG) ; inferior 

 apophyses of third united to form a strong median spine ; 

 pra2cauilals with parapoj)hyses from the fourtli ; ribs, except 

 the first, on parapojjhyses. 



Tanganyika, Congo, and West African rivers from Gambia 

 to Liberia. 



Eiglit species. 



In all the gill-rakers are short and broad, and there is a 

 well-developed papillose pad on each side of the roof of the 

 pharynx. 



The species differ considerably in tlie pharyngeal dentition 

 and in the size and form of the lower pharyngeal })late. 

 2'. microdon (fig. 1, A) and T. mylodon (fig. 1, B) are two 

 extremes ; in the former the lower pharyngeal is a compara- 

 tively small and weak plate (depth about \ maximum width), 

 with numerous small slender bicuspid teeth and with a group 

 of moderately enlarged, circular, blunt teeth occupying the 

 middle and posterior third of the dontigerous area. lu 

 T, mylodon the lower pharyngeal is large and massive (depth 

 about ^ maximum width) and is nearly covered with very 

 strong, circular, flat teeth, small bicuspid teeth appearing only 

 near the posterior angles. 



The species may be arranged according to the modifications 

 of the pharyngeal dentition as follows : — 



I. Enlarged rounded teeth of lower pha- 

 ryngeal confined to posterior third of 



dentigerous part of plate microdon. 



II. Enlarged rounded teeth of lower pha- 

 ryngeal confined to posterior half of 

 dentigerous part of plate lateralis, jentinki. 



III. Enlarged rounded teeth of lower pha- 



ryngeal extending forward on anterior 

 part of plate ; small slender teeth at 

 outer edges and near posterior angles . bangwelensis, iyifermediiis, 



IV. Enlarged rounded teeth covering nearly [labrodon,polyU'pis. 



the whole plate ; small slender teeth 



only at posterior angles mi/lodon. 



The enumeration of the number of scales in a longitudinal 

 series and of gill-rakers on the lower part of the anterior arch 

 will assist the identification of the species: — 



.33 to 35 scales ; 15 or 10 gill-ralcers 1. microdon. 



32 to 35 scales ; 17 or 18 gill-iakors 2. lateralis. 



40 to 45 scales ; 13 to 15 gill-rnkers 3. jentinki. 



37 or 38 scales ; 14 or 15 gill-rakers 4. baw/welensis. 



39 or 40 scales ; 12 or 13 gill-rakers 5. intermedins. 



33 or 34 scales; 18 or 19 g-ill-rakers <i. labrodon. 



55 to GO scales ; 1 2 to 1 5 gill-rakors 7. polylepin. 



40 or 41 scales : 17 or 18 gill-rakers 8. viylodvn. 



