BuLLEE. — On the Species of the Genus Ocyclroinus. 213 



Art. XXIV. — On the Species forming the Genus Ocydromus, a peculiar Group 



of brevi-pennate Rails. By Walter L. Buller, C.M.G., Sc.D., F.L.S. 



[Bead before the Wellington Philosophical Society, 12th Januanj, 1878.] 



Although as a group tlie limits of the genus Ocydromus are sufficiently well 

 defined, considerable difficulty lias been experienced in determining the 

 species. Every naturalist who has studied the subject appears to have 

 . arrived at some different conclusion as to the number of constant forms ; 

 and where the variances as to size and plumage are so well maintained it is 

 difficult to avoid drawing specific distinctions. If, however, it can be shown 

 that all these extreme forms graduate in a series, or, in other words, run 

 into one another, it becomes impossible to find any fixed aberrant characters. 

 Without professing to be able yet to place the matter beyond all dispute, 

 I venture to think that the series of specimens which I have the honour 

 to exhibit this evening affords pretty strong evidence that several of the 

 so-called species in the South Island must be united under the name of 

 Ocydromus aiistralis. 



In my " Birds of New Zealand," I admitted only three well-ascertained 

 species as inhabiting New Zealand — namely, 0. earli, 0. australis, and O. 

 fuscus. 1 mentioned in the introduction to that work that, although Dr. 

 Finsch recognized a fourth (0. troylodytes, Gmel.), I was unable to draw 

 any specific line. Nevertheless, I pointed out very fully, in my account 

 of the South Island wood-hen, the great variation both as to size and 

 markings which that species exhibits, especially among birds from 

 different localities. 



Captain Hutton, in an article on the New Zealand Wood-hens, read 

 before this Society* in September, 1873, agreed with Dr. Finsch in 

 admitting 0. troglodytes, and added two more species of his own under the 

 names of 0. hectori and 0. Jinschi. He further described a "variety or 

 immature" example of this last-named species, which he suggests may 

 "possibly be identical with GalUrallus hrachypterus, Lafr." 



Dr. Finsch, in a paper t written the year following, professes to identify 

 Ocydromus troglodytes with the 0. australis of my text, page 170, but not 

 the plate; of 0. hectori he remarks, "I consider this a good s^Decies after 

 having compared a typical specimen ;" and of 0. finschi he says that, 

 having examined the type, he considers it a good species, although not 

 without some suspicion that it may prove to be a variety of 0. fuscus. He 

 confuses Ocydrom.us australis, Sparrm., with the well-known 0. earli; and 

 with respect to the latter in Hutton's list, he makes the following singular 

 statement: — "Dr. Buller, in his great work, unfortunately does not mention 



* " Trans. N.Z. Inst.," VH., p. 110. t " Trans. N.Z. Inst.," VH., p. 226. 



