( 267 ) 



systematic position of Rallus dieffenbacJdi. In the first place, it is clear that it can 

 only be refen-ed to liallus in the wide Linnaean sense of that term ; and, in the 

 second, it is clearly not congeneric with Cdbalus modestiis, since the two are widely 

 different in many characters, both external and internal. The chief of these differ- 

 ences are— (1) the whole plumage of C. modestvs is much looser than in R. dieffenbachii, 

 owing to the almost complete absence of barbules ; (2) the beak is relatively much 

 lorger and more slender in the smaller bird, and is less sharply decurved at the 

 extremity ; (3) the sternum in Cahalus modestus is very much more reduced, the 

 keel being almost obsolete, while in Dieflenbach's rail it is fairly well develojieJ, 

 The general form of the bone is also different in the two species. 



Hutton and Buller have both pointed out that, in the general style and 

 colouring of the plumage, R. dieffenbachii is somewhat similar to Hypotaenidla, 

 but the difference in the form of the beak, in the proportions of the metatarsus, and 

 in many other osteological characters, exclude it from that genus; and for similar 

 reasons it cannot be regarded as an Ocydromus. This being the case, it seems 

 necessary to introduce a new generic term for this species, and I therefore propose 

 the name Nesolimnas, the only species of which is N. dieffenhac/iii* 



It is unfortunate that none of the bones of the type-.specimen of this species 

 were preserved by its discoverer, but this deficiency can now be made good, since 

 in the collection at Tring there is an almost perfect skeleton which clearly belongs 

 to this rail, the form of the beak and metatarsus being identical with those of the 

 type. In addition to this valuable specimen, there are also skulls and other [wrtions 

 of the skeleton of many other individuals. 



The skull (PI. X., figs. 3, 4) is very similar to those of Ocydromus, the so-called 

 Cabalus sylvestris, and Hypokmnidiii celebensis, to which there is much greater 

 similarity than to the skull of the smaller H. philippiaensis. In the cranial region 

 there is a very near approach to Ocydromus, the only noticeable differences between 

 the two being that in the New Zealand bird the lambdoidal ridge is a little more 

 prominent and the paroccipital processes smaller. In the larger size of these 

 processes, Cabahis(?) sylvestris and Erythromachus are more similar to the Chatham 

 Island bird, to which the former of these species is also similar in its larger post- 

 orbital processes. In the base of the skull also there are no marked differences 

 from the same region in Ocyd/romus, although the basi-temporal platform may be 

 slightly less prominent and the pre-temporal wing rather more developed. In 

 AV?/(Ara»i,«c/«ts the basi-temporal platform is much more prominent. The iuterorbital 

 region is almost exactly the same as in Gahahis sylvestris and Ocydromus. 



The posterior portion of the margin of the orbits is truncated bj' the impression 

 of a supra-orbital gland, but to a less extent than in Ocydromus; in this respect, 

 and also in the greater width of the interorbital region of the frontals, C(ibalus{?) 

 sylvestris comes nearest to the present species. 



It is in the form of the beak that Nesolimnas differs most widely from the other 

 forms : the whole culmen is convex from before backwards, and the tip is sharply 

 decurved. In Ocydromus the beak is only slightly curved; otherwise in its relative 

 size and in the proportions of its naiial and pre-narial regions it is very similar to 

 that of the present species. 



* In Tart I,, not having hail occasion to consider the syslumatic position of this l)inl, I followoil rec-ent 

 writera in employing the n.ame Cahalwi dlcffen.iachii for it, and 1 am indelitcd to Professor liulton for 

 ilrawiug my attention to this point. Numerous measurements of the slieleton of this species have been 

 already given in I'an 1. undoi the name Cabalus. 



