672 MR. G. A. BOULENGER ON 



fell off ; the pieces somewhat resembled the wing-cases of a large 

 beetle, being semi-transparent and of a clear orange-colour. 



Dr. Francis Ward, F.Z.S., showed a number of photographs 

 and diagrams illustrating a method of observation of fishes, birds, 

 and mammals under the water, the principle being that the 

 subjects under consideration were illuminated by natural light, 

 and the observer, being in a dark chamber in the water, was not 

 seen. The appearance of black-feathered birds was shown ; 

 these, by carrying down air-bubbles among the feathers, were 

 converted into reflectoi-s : and a Water-Hen was shown bright red 

 and then green as it reflected the different surroundings in 

 which it had been placed. Otters and Seals were also shown as 

 seen under the water. The demonstration was illustrated by 

 numerous slides and by the cinematograph. 



PAPERS. 



37. On a Collection o£ Fishes made by Mr. A. Blayney 

 Percival in British East Africa to the East of Lake 

 Baringo. Bj G. A. Boulenger, F.R.S., F.Z.S.* 



[Received April 2, 1912 : Read May 7, 1912.] 



(Plates LXXYIII.-LXXX.t) 



Index. 



Systematic : Page 



Labeo percivali, syi. li 673 



Sarhus argyrotmnia, s^i. x\ 674 



S. mimus, sp. n 674 



AmpMlius oxyrhinus, s,\>. n 675 



Tilapia per civali, sj). n 676 



The collection here reported upon, presented to the British 

 Museum by Mr. Blayney Percival, is of special importance as 

 coming from a district the fishes of which had not been collected 

 before, from a watershed of its own without any communication 

 with sea. The river called Eusso Nyiro, or Guaso JSTyiro, quite 

 distinct from the Southern Guaso ISTyiro in German East Africa, 

 takes its source to the east of Lake Baringo, separated from it 

 and from Lake Rudolf by hill-ranges 1000 to 1500 feet higher 

 (4000 to 5000 feet above sea-level) and is lost in the Lorian 



* Published by pemiissinii of the Trustees of the British Museum, 

 t For explanation of the Plates see p. 676. 



