THE BIRDS OF AUSTRALIA. 
are admitted by Professor Reichenow, and after a prolonged study, I think that, 
for the present at least, no alteration is advisable. I must, however, state that 
in the large series which I have examined in the British Museum and in the 
Rothschild collection, it has been impossible to define, from the characters 
of the width of the bill and its lamellae, where one species ends and another 
begins, the connection between the broad-billed Prion vittatus and the thin- 
billed P. desolatus being practically complete, if a large series is examined. So 
far as is known, no two forms of these Blue Petrels nest on the same island, 
but our knowledge is so limited that it would be unwise to alter the present 
determination. ’ ’ 
Previously dealing with the species named Procellaria ccerulea by Gmelin, 
the author of the Monograph had written (p. 281) : “ In colour and markings 
H. ccBrulea resembles the species of the genus Prion, but differs from them in the 
shape of the tail, which forms a distinguishing character. It has also been 
separated from Prion by reason of the supposed absence of the lamellae near 
the base of the upper mandible ; a close examination, however, shows that the 
lamellae are present though very minute, so that this character does not hold 
good ; but I cannot unite the two genera, as has been done by Reichenow and 
W. L. Sclater, on account of the difference in the tail, which in Halobcena is 
square, while m Prion it is wedge-shaped.” Considering that the difference 
in the shape of the tail was so small, and the fact that the bill was admitted to be 
of the Prionitic type, I indicated in the E7nu (Vol. X., p. 320, 1911) my con- 
clusion that the genus Halobcena should be merged in Prion ; there was obviously 
much greater difference between P. vittatus and P. desolatus than between 
P. desolatus and P. ccerulus, if the colour of the tail were ignored. 
The monographic study I have since made of this group, has caused me 
to altogether modify that view, and I here put forward the results of my 
investigations. 
I have enjoyed the advantage of studying the whole of the British Museum 
collection which includes the types of P. forsteri Smith, P. hanJcsi Smith, 
P. turtur Smith, P. magnirostris Gould, P. hrevirostris Gould, P. rossi Bonaparte ; 
typical specimens (paratypes) of P. ariel Gould and P. australis Potts ; and 
topo types of P. vittatus Gmelin and P. desolatus Gmelin. These include all the 
forms that have been named. In conjunction, I have studied the very fine 
collection of examples, mostly from New Zealand, in the Rothschild Museum, 
Tring, as the Hon. Walter Rothschild, with his usual generosity, has placed 
them at my disposal. My own series helped to fill up some gaps, and Mr. Eagle 
Clarke once more loaned me specimens obtained by the Scottish Antarctic Expe- 
dition, for which thanks are due. Bound up intimately with the literature of 
these birds is the avifauna of South Africa, as in the Zoology of South Africa, by 
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