494 PEOCELLARIID^ DIOMEDBA 



under wing-coverts also slightly mottled with grey. Bill black; 

 feet bluish. 



Length about 8-5; wing 4-7; tail 1-5; culnieii-7; tarsus 1-0; 

 middle toe I'O. 



Distribution. — This Diving Petrel is found throughout the 

 southern part of the Indian Ocean and is especially abundant at 

 Kerguelen and the Crozet Islands, whence the South African 

 Museum possesses examples. A Diving Petrel was observed by 

 Mr. Green off the Cape of Good Hope when homeward bound from 

 Australia. This is the only record of its occurrence about the 

 South African seas. 



Habits. — This bird is interesting as an example of special modifi- 

 cation of the Petrel type. It has lost the power of strong flight 

 possessed by its relatives, but has acquired a great facility for 

 diving, during which process it uses its wings to assist in its pro- 

 gression under water. 



It breeds on Kerguelen, laying a single egg at the end of a long 

 burrow. 



Subfamily IV. DIOMBDEIN^. 



Nostrils lateral, separated by a wide culmen, each in a separate 

 sheath opening forwards ; margin of the sternum uneven, the 

 sternuna short compared with its width ; no basipterygoid processes ; 

 humerus pneumatic ; first primary the longest ; ambiens muscle 

 and caeca present ; hind toe absent or very rudimentary. 



Genus I. DIOMEDEA. 



Type. 

 Diomedea, Linn. Syst. Nat. 12th ed. i, p. 214 (1766) D. exulans. 



Bill stout and strong, longer than the head ; formed of four 

 pieces, the cuhninicorn along the culmen, the pair of latericorns on 

 either side and the apicorn at the apex ; culminicorn bordering the 

 latericorn, behind and in front of the nostrils ; no longitudinal 

 groove along the lower mandible ; line of the lower edge of the 

 lower mandible almost straight, the tip not downcurved ; nostrils 

 on either side of the culminicorn between it and the latericorn, 

 surrounded by a separate bony sheath and opening forwards ; wings 

 very long when outstretched, owing chiefly to the great length of 



