The　Mammalia　of　New　Guinea　and　the　adjacent　islands；　yet　discovered；　are　only　seventeen　in　number。　Two　of　these　are　bats；　one　is　a　pig　of　a　peculiar　species　（Sus　papuensis）；　and　the　rest　are　all　marsupials。　The　bats　are；　no　doubt；　much　more　numerous；　but　there　is　every　reason　to　believe　that　whatever　new　land　Mammalia　man　be　discovered　will　belong　to　the　marsupial　order。　One　of　these　is　a　true　kangaroo；　very　similar　to　some　of　middle…　sized　kangaroos　of　Australia；　and　it　is　remarkable　as　being　the　first　animal　of　the　kind　ever　seen　by　Europeans。　It　inhabits　Mysol　and　the　Aru　Islands　（an　allied　species　being　found　in　New　Guinea）；　and　was　seen　and　described　by　Le　Brun　in　1714；　from　living　specimens　at　Batavia。　A　much　more　extraordinary　creature　is　the　tree…kangaroo；　two　species　of　which　are　known　from　New　Guinea。　These　animals　do　not　differ　very　strikingly　in　form　from　the　terrestrial　kangaroos；　and　appear　to　be　but　imperfectly　adapted　to　an　arboreal　life；　as　they　move　rather　slowly；　and　do　not　seem　to　have　a　very　secure　footing　on　the　limb　of　a　tree。　The　leaping　power　of　the　muscular　tail　is　lost；　and　powerful　claws　have　been　acquired　to　assist　in　climbing；　but　in　other　respects　the　animal　seems　better　adapted　to　walls　on　terra　firma。　This　imperfect　adaptation　may　be　due　to　the　fact　of　there　being　no　carnivore　in　New　Guinea；　and　no　enemies　of　any　kind　from　which　these　animals　have　to　escape　by　rapid　climbing。　Four　species　of　Cuscus；　and　the　small　flying　opossum；　also　inhabit　New　Guinea；　and　there　are　five　other　smaller　marsupials；　one　of　which　is　the　size　of　a　rat；　and　takes　its　place　by　entering　houses　and　devouring　provisions。
  The　birds　of　New　Guinea　offer　the　greatest　possible　contrast　to　the　Mammalia；　since　they　are　more　numerous；　more　beautiful；　and　afford　more　new；　curious；　and　elegant　forms　than　those　of　any　other　island　on　the　globe。　Besides　the　Birds　of　Paradise；　which　we　have　already　sufficiently　considered；　it　possesses　a　number　of　other　curious　birds；　which　in　the　eyes　of　the　ornithologist　almost　serves　to　distinguish　it　as　one　of　the　primary　divisions　of　the　earth。　Among　its　thirty　species　of　parrots　are　the　Great　Pluck　Cockatoo；　and　the　little　rigid…tailed　Nasiterna；　the　giant　and　the　dwarf　of　the　whole　tribe。　The　bare…headed　Dasyptilus　is　one　of　the　most　singular　parrots　known；　while　the　beautiful　little　long…tailed　Charmosyna；　and　the　great　variety　of　gorgeously…coloured　lories；　have　no　parallels　elsewhere。　Of　pigeons　it　possesses　about　forty　distinct　species；　among　which　are　the　magnificent　crowned　pigeons；　now　so　well　known　in　our　aviaries；　and　pre…eminent　both　for　size　and　beauty；　the　curious　Trugon　terrestris；　which　approaches　the　still　more　strange　Didunculus　of　Samoa；　and　a　new　genus　（Henicophaps）；　discovered　by　myself；　which　possesses　a　very　long　and　powerful　bill；　quite　unlike　that　of　any　other　pigeon。　Among　its　sixteen　kingfishers；　it　possesses　the　carious　hook…billed　Macrorhina；　and　a　red　and　blue　Tanysiptera；　the　most　beautiful　of　that　beautiful　genus。　Among　its　perching　birds　are　the　fine　genus　of　crow…like　starlings；　with　brilliant　plumage　（Manucodia）；　the　carious　pale…　coloured　crow　（Gymnocorvus　senex）；　the　abnormal　red　and　black　flycatcher　（Peltops　blainvillii）；　the　curious　little　boat…billed　flycatchers　（Machaerirhynchus）；　and　the　elegant　blue　flycatcher…　wrens　（Todopsis）。
  The　naturalist　will　obtain　a　clearer　idea　of　the　variety　and　interest　of　the　productions　of　this　country；　by　the　statement；　that　its　land　birds　belong　to　108　genera；　of　which　20　are　exclusively　characteristic　of　it；　while　35　belong　to　that　limited　area　which　includes　the　Moluccas　and　North　Australia；　and　whose　species　of　these　genera　have　been　entirely　derived　from　New　Guinea。　About　one…half　of　the　New　Guinea　genera　are　found　also　in　Australia；　about　one…third　in　India　and　the　Indo…Malay　islands。
  A　very　curious　fact；　not　hitherto　sufficiently　noticed；　is　the　appearance　of　a　pure　Malay　element　in　the　birds　of　New　Guinea。　We　find　two　species　of　Eupetes；　a　curious　Malayan　genus　allied　to　the　forked…tail　water…chats；　two　of　Alcippe；　an　Indian　and　Malay　wren…like　form；　an　Arachnothera；　quite　resembling　the　spider…　catching　honeysuckers　of　Malacca；　two　species　of　Gracula；　the　Mynahs　of　India；　and　a　curious　little　black　Prionochilus；　a　saw…　billed　fruit　pecker；　undoubtedly　allied　to　the　Malayan　form；　although　perhaps　a　distinct　genus。　Now　not　one　of　these　birds；　or　anything　allied　to　them；　occurs　in　the　Moluccas；　or　（with　one　exception）　in　Celebes　or　Australia；　and　as　they　are　most　of　them　birds　of　short　flight；　it　is　very　difficult　to　conceive　how　or　when　they　could　have　crossed　the　space　of　more　than　a　thousand　miles；　which　now　separates　them　from　their　nearest　allies。　Such　facts　point　to　changes　of　land　and　sea　on　a　large　scale；　and　at　a　rate　which；　measured　by　the　time　required　for　a　change　of　species；　must　be　termed　rapid。　By　speculating　on　such　changes；　we　may　easily　see　how　partial　waves　of　immigration　may　have　entered　New　Guinea；　and　how　all　trace　of　their　passage　may　have　been　obliterated　by　the　subsequent　disappearance　of　the　intervening　land。
  There　is　nothing　that　the　study　of　geology　teaches　us　that　is　more　certain　or　more　impressive　than　the　extreme　instability　of　the　earth's　surface。　Everywhere　beneath　our　feet　we　find　proofs　that　what　is　land　has　been　sea；　and　that　where　oceans　now　spread　out　has　once　been　land；　and　that　this　change　from　sea　to　land；　and　from　land　to　sea；　has　taken　place；　not　once　or　twice　only；　but　again　and　again；　during　countless　ages　of　past　time。　Now　the　study　of　the　distribution　of　animal　life　upon　the　present　surface　of　the　earth；　causes　us　to　look　upon　this　constant　interchange　of　land　and　seathis　making　and　unmaking　of　continents；　this　elevation　and　disappearance　of　islandsas　a　potent　reality；　which　has　always　and　everywhere　been　in　progress；　and　has　been　the　main　agent　in　determining　the　manner　in　which　living　things　are　now　grouped　and　scattered　over　the　earth's　surface。　And　when　we　continually　come　upon　such　little　anomalies　of　distribution　as　that　just　now　described；　we　find　the　only　rational　explanation　of　them；　in　those　repeated　elevations　and　depressions　which　have　left　their　record　in　mysterious；　but　still　intelligible　characters　on　the　face　of　organic　nature。
  The　insects　of　New　Guinea　are　less　known　than　the　birds；　but　they　seem　almost　equally　remarkable　for　fine　forms　and　brilliant　colours。　The　magnificent　green　and　yellow　Ornithopterae　are　abundant；　and　have　most　probably　spread　westward　from　this　point　as　far　as　India。　Among　the　smaller　butterflies　are　several　peculiar　genera　of　Nymphalidae　and　Lycaenidae；　remarkable　for　their　large　size；　singular　markings；　or　brilliant　coloration。　The　largest　and　most　beautiful　of　the　clear…winged　moths　（Cocytia　d'urvillei）　is　found　here；　as　well　as　the　large　and　handsome　green　moth　（Nyctalemon　orontes）。　The　beetles　furnish　us　with　many　species　of　large　size；　and　of　the　most　brilliant　metallic　lustre；　among　which　the　Tmesisternus　mirabilis；　a　longicorn　beetle　of　a　golden　green　colour；　the　excessively　brilliant　rose…chafers；　Lomaptera　wallacei　and　Anacamptorhina　fulgida；　one　of　the　handsomest　of　the　Buprestidae；　Calodema　wallacei；　and　several　fine　blue　weevils　of　the　genus　Eupholus；　are　perhaps　the　most　conspicuous。　Almost　all　the　other　orders　furnish　us　with　large　or　extraordinary　forms。　The　curious　horned　flies　have　already　been　mentioned；　and　among　the　Orthoptera　the　great　shielded　grasshoppers　are　the　most　remarkable。　The　species　here　figured　（Megalodon　ensifer）　has　the　thorax　covered　by　a　large　triangular　horny　shield；　two　and　a　half　inches　long；　with　serrated　edges；　a　somewhat　wavy；　hollow　surface；　and　a　faun　median　line；　so　as　very　closely　to　resemble　a　leaf。　The　glossy　wing…coverts　（when　fully　expanded；　more　than　nine　inches　across）　are　of　a　fine　green　colour　and　so　beautifully　veined　as　to　imitate　closely　some　of　the　large　shining　tropical　leaves。　The　body　is　short；　and　terminated　in　the　female　by　a　long　curved　sword…like　ovipositor　（not　seen　in　the　cut）；　and　the　legs　are　all　long　and　strongly…　spined。　These　insects　are　sluggish　in　their　motions；　depending　for　safety　on　their　resemblance　to　foliage；　their　horny　shield　and　wing…coverts；　and　their　spiny　legs。
  The　large　islands　to　the　east　of　New　Guinea　are　very　little　known；　but　the　occurrence　of　crimson　lories；　which　are　quite　absent　from　Australia；　and　of　cockatoos　allied　to　those　of　New　Guinea　and　the　Moluccas；　shows　that　they　belong　to　the　Papuan　group；　and　we　are　thus　able　to　define　the　Malay　Archipelago　as　extending　eastward　to　the　Solomon's　Islands。　New　Caledonia　and　the　New　Hebrides；　on　the　other　hand；　seem　more　nearly　allied　to　Australia；　and　the　rest　of　the　islands　of　the　Pacific；　though　very　poor　in　all　forms　of　life；　possess　a　few　peculiarities　which　compel　us　to　class　them　as　a　separate　group。　Although　as　a　matter　of　convenience　I　have　always　separated　the　Moluccas　as　a　distinct　zoological　group　from　New　Guinea；　I　have　at　the　same　time　pointed　out　that　its　fauna　was　chiefly　derived　from　that　island；　just　as　that　of　Timor　was　chiefly　derived　from　Australia。　If　we　were　dividing　the　Australian　region　for　zoological　purposes　alone；　we　should　form　three　great　groups：　one　compr