164 Mr. C. T. Regan on the African 
anteriorly. Vertebras 29-32 (15-16+4+14-16); inferior 
apophyses of third united to form a strong median spine ; 
preecaudals with parapophyses from the fourth; ribs, except 
the first, on parapophyses. 
Tanganyika, Congo, and West African rivers from Gambia 
to Liberia. 
Hight 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 the pharyngeal dentition 
and in the size and form of the lower pharyngeal plate. 
T. microdon (fig. 1, A) and 7. 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 dentigerous area. In 
T. mylodon the lower pharyngeal is large and massive (depth 
about 4 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. 
{I. Enlarged rounded teeth of lower pha- 
ryngeal confined to posterior half of 
dentigerous part of plate .......... lateralis, jentinkt. 
III. Enlarged rounded teeth of lower pha- 
ryngeal extending forward on anterior 
part of plate; small slender teeth at 
outer edyes and near posterior angles, bangwelensis, intermedius, 
LV. Enlarged rounded teeth covering nearly [labrodon, polylepis. 
the whole plate; small slender teeth 
only at posterior angles .......... .. mylodon. 
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 16 gill-rakers............ wea, Litenecrodon: 
32 to 86 scales; 17 or 18 gill-rakers..............0. 2. lateralis. 
40 to 45 scales; 13 to 15 gill-rakers................ 3. gentinkt, 
87 or 88 scales; 14 or 15 gill-rakers................ 4, bangwelensis. 
39 or 40 scales; 12 or 13 gill-rakers................ 5. intermedius. 
33 or 34 scales; 18 or 19 gill-rakers ..............4. 6. labrodon. 
55 to 60 scales; 12 to 15 gill-rakerg .............00. 7. polylepis. 
AO or 41 scales; 17 or 18 gill-rakers................ 8. mylodon. 
