676 ON FISHES FROM BRITISH EAST AFRICA. 



20. TiLAPIA PERCIVALI, Sp. n. (PI. LXXIX. fig. 3.) 



Depth of body equal to length of head, 2| times in total length. 

 Head about twice as long as broad ; snout rounded, with straight 

 or slightly convex upper profile, a little broader than long, | post- 

 ocular part of head ; eye 3g (young) to 4 times in length of head, 

 greater than prseorbital depth ; mouth large, | width of head, 

 extending to below anterior border of eye ; lips very strongly 

 developed ; teeth moderately slender, in 3 or 4 series, 40 to 50 

 in outer series of upper jaw ; 2 series of scales on the cheek, width 

 of scaly part rather less than diameter of eye. Gill-rakers short, 

 13 or 14 on lower part of anterior arch. Dorsal XIII-XY 11 ; 

 spines increasing in length to the last, which measuies |- length of 

 head ; longest soft rays | length of head. Anal III (exceptionally 

 IV) 9-10; third spine ^ length of head. Pectoral about | length of 

 head, not reaching origin of anal. Ventral reaching vent or anal. 

 Caudal rounded, subtruncate. Caudal peduncle deeper than long. 

 Scales cycloid, 30-31 — ? : lateral lines 1^:^, Dark brown, with 



J ' 12 ' :3-16 ' 



black vertical bars on the body, or entirely black. 



Total length 75 mm. 



Hot springs at Chandler Falls, Northern Eusso Nyiro, 2500 ft. 

 Caught in water about 100° Fahr. 



Near allies of this new Tilapia are T. alcalica Hilgend. from 

 alkaline water in volcanic holes near the Ngiu'uman Salt Lake, 

 into which the Southern Guaso Nyiro flows, on the boundary of 

 British and German East Africa, and T, graJiami Blgr. from Lake 

 Magade, a perfectly isolated hot soda lake in the Rift Valley, 

 British East Africa, not far from the Southern Guaso Nyiro. 

 The former has, like T. percivali, D. XIII 11, but the scales on 

 the cheek are in two series and the caudal is truncate ; the latter 

 has D. XI 11-12, 3 series of scales on the cheek, and the caudal 

 peduncle is deeper than long. 



EXPLANATION OP THE PLATES. 



Plate LXXVIIL 

 Laheo percivali, p. 673. f nat. size. 



Plate LXXIX. 



Pig. ] . Barhus argyrotcenia, p. 674. 



2. „ mimtis, p. 674. 



3. Tilapia percivali, p. 676. 



Plate LXXX. 



Ampliilius o.ri/rJiitius, p. 675. 



