AFRICAN REGION. 227 



noid senera inhabiting similar localities, and the lakes into 

 which the alpine rivers pass, such as Oreimis, Schizothorax, 

 Ptychdbarlus, Schizopygopsis, Diptychus, Gymnocypris, are dis- 

 tinguished by peculiarly enlarged scales near the vent, the 

 physiological use of which has not yet been ascertained. 

 These alpine genera extend far into the Europo-Asiatic 

 region, where the climate is similar to that of their southern 

 home. No observations have been made by which the alti- 

 tudinal limits of fish life in the Himalayas can be fixed, 

 but it is probable that it reaches the line of perpetual snow% 

 as in the European Alps which are inhabited by Salmonoids. 

 Griffith found an Oreinus and a Loach, the former in abun- 

 dance, in the Helmund at Gridun Dewar, altitude 10,500 

 feet ; and another Loach at Kaloo at 11,000 feet, 



B. The African Eegion comprises the whole of the 

 African continent south of the Atlas and the Sahara. It 

 might have been conjectured that the more temperate climate 

 of its southern extremity would have been accompanied by a 

 conspicuous difference of the fish-fauna. But this is not the 

 case ; the difference between the tropical and southern parts 

 of Africa consists simply in the gradual disappearance of spe- 

 cifically tropical forms, whilst Siluroids, Cyprinoids, and 

 even Labyrinthici penetrate to its southern coast; no new 

 form has entered to impart to South Africa a character dis- 

 tinct from the central portion of the continent. In the north- 

 east the African fauna passes the Isthmus of Suez and pene- 

 trates into Syria ; the system of the Jordan presenting so 

 many African types that it has to be included in a description 

 of the African region as well as of the Europo-Asiatic. This 

 river is inhabited by three species of Chromis, one of Hemi- 

 chromis, and Clarias macr acanthus, a common fish of the 

 Upper Nile. This infusion of African forms cannot be ac- 

 counted for by any one of those accidental means of dispersal, 



