atricapilla_, from which last it is almost impossible to distinguish the _A. javanica_, of wide range throughout Asia and its islands, while other species, less closely related, occur elsewhere as _A. flavicollis_--one form of which, _A. gouldi_, inhabits Australia. [Illustration: FIG. 2.--Bittern.] The true bitterns, forming the genus _Botaurus_ of most authors, seem to be fairly separable, but more perhaps on account of their wholly nocturnal habits and correspondingly adapted plumage than on strictly structural grounds, though some differences of proportion are observable. The common bittern (q.v.) of Europe (_B. stellaris_), is widely distributed over the eastern hemisphere.[3] Australia and New Zealand have a kindred species, _B. poeciloptilus_, and North America a third, _B. mugitans_[4] or _B. lentiginosus_. Nine other species from various parts of the world are admitted by Professor Schlegel, but some of them should perhaps be excluded from the genus _Botaurus_. Of the night-herons the same author recognizes six species, all of which may be reasonably placed in the genus _Nycticorax_, characterized by a shorter beak and a few other peculiarities, among which the large eyes deserve mention. The first is _N. griseus_, a bird widely spread over the Old World, and not unfrequently visiting England, where it would undoubtedly breed if permitted. Professor Schlegel unites with it the common night-heron of America; but this, though very closely allied, is generally deemed distinct, and is the _N. naevius_ or _N. gardeni_ of most writers. A clearly different American species, with a more southern habitat, is the _N. violaceus_ or _N. cayennensis_, while others are found in South America, Australia, some of the Asiatic Islands and in West Africa. The Galapagos have a peculiar species, _N. pauper_, and another, so far as is known, peculiar to Rodriguez, _N. megacephalus_, existed in that island at the time of its being first colonized, but is now extinct. [Illustration: FIG. 3.--Boatbill.] The boatbill, of which only one species is known, seems to be merely a night-heron with an exaggerated bill,--so much widened as to suggest its English name,--but has always been allowed generic rank. This curious bird, the _Cancroma cochlearia_ of most authors, is a native of tropical America, and what is known of its habits shows that they are essentially those of a _Nycticorax_.[5] Bones of the common heron and bittern are not uncommon in the peat of the East-Anglian fens. Remains from Sansan and Langy in France have been referred by Alphonse Milne-Edwards to herons under the names of _Ardea perplexa_ and _A. formosa_; a tibia from the Miocene of Steinheim am Albuch by Dr Fraas to an _A. similis_, while Sir R. Owen recognized a portion of a sternum from the London Clay as most nearly approaching this family.