'^J^lic Qiiiitcniary laiiiiu ol .Maine iiidicali's a iiiiicli nunc piiicly aictn- assciu- 

 hlain' llian is at presrnl to l)c fonnd.* 'I'iiis is also tlif rase willi tlir Scaiuli- 

 navian Quaternary liuina, accordiny to tiie researches ol tlic late I'rol'. M. 

 Sars As wo liave het'ore s'now n, in the I'ssa}' just referred to, the eirenni- 

 iiolar marine iiiuna extends down aloni^' tlie eoast ol' Nortiieastern America 

 and ol Europe, and the forms common to tiie two shores are ciicnmpolar 

 forms, memhers of the ciicumpohir /.o(ih)gical reahn. I'lnrope. in all piol)ii- 

 l)ilitv, did not borrow any of her specitic forms fr(Mn America: hut both have 

 i)een. in part, peopled tVom a purely circumpolar fauna. if ihere has iieeii 

 anv borrowing, it has iieeu on the pai'l of ]<]urope, since the lossil musk- 

 shee|) {Oi^ihoti) of France; and ('(Mitral JMirope is said to Ite identical wilii 

 the uuislv-sheep of arctic America. 80. also, on the coast of Northeastern 

 Asia and Alaska are circumpolar forms, which have evidently ijcen borne i»y 

 arctic currents down each coast. The forms which an; identical (u- repre- 

 sentative on those two coasts are s[)ccies derived from the circumpolar fauna: 

 so the forms which are so strikingly similar in Xortheru ,la|)au to those on 

 the coast of New England are, if we mistake no<, also derivi^d from the 

 nortiiward. From the consideration of these facts, we are led to accept the 

 conclusion that congeneric forms occurring on tlie I'acilic slope of Nmlh 

 America, as well as Europe and Asia, are the remnaulsof a southward migra- 

 tion from polar lands during Tertiary times, and, in proportion to the iiiirh 

 anticpiity of the migrations, there have been changes and extinctions, causinir 

 the present anomalies in the distribution of organized Ix'inas wiiich are now 

 so diliicult to account for on any other hypothesis. For this reason, it is not 

 improl)al)le that those species of insects which are nuuc or less cosmopolite 

 (and independently .so of human aLrency) are the mo.<t ancient, just as some 

 forms taxonomically the most remote are remnants of eaili(;r geoloijical 

 periods. For example, the curious anomalies in the geographical <listril)ution 

 of Limulns, the genus only occurring on tlie eastern coasts ol Asia and 

 North America, accord with its isolation from other Crustacea. Geological 

 extinction lias gone hand in hand with geogra|)hical isolation. It was not an 

 uncommon form in Europe in the Jurassic period, aiul was preceded by other 

 Merostomata in the Pala;ozoi(^ periods. 



• " Glacial Pbeuomena of Labrador and Mainn," by A. S. Packard, .jr., in JKnioirs of Boston Society 

 of Natural History, i, 1865. 

 75 P H 



