AVIFAUNA OF LAYS AN, ETC. 



05 



THE GENUS HETERORHYNCHUS. 



The type of this genus is H. olivaceus, which is identical with II. lucidus. In all its chief 

 characters it agrees with Ilemignathus, except in the formation of the bill. The upper 

 mandible is strong at base, but narrow and thin at tip, not so long as in HemignatMis, 

 and quite different from the lower mandible; the latter is only about half as long 

 as the upper, and rather strong. " The tongue is consequently shorter than in 

 Ilemignathus, and less tubular, being intermediate in structure between those of Ilimatione 

 and Vestiaria. The stomach of II. wilsoni is, as in Ilemignathus procerus, quadrangular 

 and strong. The convolutions of the intestinal canal are like those of II. procerus ; but 

 the central spiral has one twist more, owing to the greater length of the gut, the total 

 length being (in H. wilsoni) as much as 25*5 centim., giving the relative length of 6." (See 

 Gadow, in ' Aves Hawaiienses,' part ii. p. 15.) 



The species of the genus Heterorhynchus can be divided into two groups — one, containing 

 only H. wilsoni, with the under mandible quite straight and very strong, much like a 

 Woodpecker's under mandible ; and the other, containing three species, with the under 

 mandible curved and following the curve of the upper. 



One species is known from each of the islands of Hawaii, Maui, Oahu, and Kauai. 

 Prom its geographical position one would expect that Kauai, being most isolated and 

 separated from the other islands by a deej) channel, much more than twice as broad as the 

 Alenuihaha Strait between Hawaii and Maui, would have the most aberrant form ; but 

 instead of this we find that the species from Kauai and Maui are the most nearly allied, 

 between them a much different form occurs on Oahu, and the most aberrant on Hawaii. 



There is no reason why Lanai and Molokai should not have been, or still be, the habitat of 

 a species of Heterorhynchus, which might be the same as my II. affinis, or an undescribed 

 species. 



Key to the Genus Heterorhynchus. 



A. Under mandible straight H. wilsoni. 



B. Under mandible curved. 



a. A very distinct superciliary stripe ; head green H. lucidus. 



b. No distinct superciliary stripe; head yellow. 



a'. Colour of head gradually merging into that of the back H. kanapepe. 



b'. Colour of head separated somewhat abruptly from that of the back, which is 



quite different from that of the head H. affinis. 



