SHEATH-BILLS. 



93 



southern hemisphere, they being chiefly found on the islands adjacent to the southern 

 extremity of South America, -- Kerguelen's Island and the Crozets. 



The most remarkable and quite unique structure of these birds is the saddle-shaped 

 horny sheath, overlying the base of the culmen and partly concealing the nostrils, - 

 hence the name sheath-bill. This sheath is continued backward into a kind of IKK id 

 covering the face, being naked and carunculated on the lores and ocular region, but 

 densely feathered on the forehead, as represented in the accompanying cut. The bill 

 and the naked skin are yellowish in Chionis alba, black in Ch. minor, the latter also dif- 

 fering considerably in the shape of the sheath. On the carpus is a knob-shaped promi- 

 nence which supports a wing spur. The plumage of both species is dazzlingly white all 

 over. The feet are covered with a reticulate skin, both in front and behind ; four 

 toes are present, having the normal 



FIG. 40. Head of Chionis alba, white sheath-bill. 



number of phalanges, which diminish in 

 size from the basal to the terminal one, 

 only very small webs connecting the an- 

 terior toes at the base. 



The habits of Ch. minor, which in- 

 habits Kerguelen's Island and the Cro- 

 zets, unless the bird of the latter, which 

 seems to have darker legs, is a separable 

 form, have been only very recently in- 

 vestigated, and specimens are still very 

 rare in collections. The recent Ameri- 

 can, English, and German Transit-of- Venus expeditions to that desolate shore have 

 furnished us with excellent descriptions of the manners and peculiarities of that 

 species. All observers agree as to their resemblance in appearance, manner of 

 caressing one another, gait and flight, to pigeons or ptarmigans. Dr. Kidder saw 

 them eat only soft, green seaweed when in the wild state, but Mr. Eaton, of the 

 English party, asserts that they also feed on mussels and isopod Crustacea, and that 

 they greedily devour shags' and penguins' eggs. The former observer enlarges upon 

 their great tameness and curiosity. They nest in holes between or behind rocks, laying- 

 one to three eggs, which somewhat resemble those of the oyster-catcher, toward the 

 end of December and the beginning of January. The chicks are covered with a uni- 

 form slate-gray down. Males and females are alike, but the loral caruncle is smaller 

 in the latter, which also has the carpal spine smaller and flesh-colored, and not black 

 as has the male. The young birds are like the adults, but have pink tips to their 



wings. 



The THINOCORID.E, a family consisting of two genera, Thinocorus and Attagis, with 

 together a little more than half a dozen species, inhabit South America down to 

 Magelhaen's Strait and the Falkland Islands ; in the tropical portions they occur, how- 

 ever, only in the elevated regions. Externally they resemble, in size and color, quails 

 or partridges, the analogy being carried so far as to also embrace the shortness of the 

 legs, but the long and pointed wings, with the long secondaries, at once suggest their 

 affinity with the Scolopacoid birds. At first they were regarded as Gallinaceous birds, 

 while some authors referred them to the pigeons or sand-grouse ; but the Limicoline 

 pterylosis and the many obvious structural characters soon secured place for them 

 among the Gralla?. Finally, Professor Garrod, in 1874, settled the question beyond 

 dispute, by giving an account of all their anatomical characteristics. From his inves- 



