_ 4 — 



collections, and interesting as a survivor of a family of 

 fishes abundantly represented in the earlier seas, of our 

 planet. 



Fig. 1. — Polypterus bichir (./jii ^' ) 



Lake Menzaleh. 



Lake Menzaleh, communicating, as it does, with the 

 sea through an ancient mouth of the Nile (Tanaitic), and 

 with the Nile itself through the agency of several agri- 

 cultural canals, is a brackish lake. The saltness of its 

 waters varies at different points and at different seasons. 

 Near its sea entrance and towards its southeastern moiety, 

 its density is equal to, and in isolated spots, more than, 

 that of sea water, while the portions of the lake near the 

 fresh water inlets are comparatively fresh. From its 

 physical conditions, therefore, it is not surprising that it 

 should contain both salt and fresh- water fish. The former 

 include chieflv littoral forms from the Mediterranean, and 

 the Nile supplies the freshwater species. To my know- 

 ledge there are no fish peculiar to the lake. 



Naturally there is a preponderance of saltwater species 

 in the Salter parts of the lake, and the converse is equally 

 true. At the period of high Nile the influx of floodwater 

 aSFects -the salinity of portions of the lake, and therefore 



