Simmons, Remarks about the Relations of the Floras etc. 
183 
the tertiary origin of every species and genus of the present 
floras of the regions in question, as in many cases our present 
knowledge of their distribution will probably prove incomplete, 
but in many other instanees I think it must be possible to 
settle alreadv now the question about the tertiary area. 
At first I will take into consideration such genera as must 
have had their sole home or at least liave been principally re- 
presented in the tertiary Polar Sea, as can be concluded from 
Table VIII. 
Such are: 
Streblonema 
Maria 
Pl/ycocelis 
Agarum 
Chaetopteris 
Laminaria 
Drsmotrichum 
Lithoderma 
Punctaria 
Fucus 
Coilodesme 
Phyüophora 
Plileospora 
Cystoelonium 
Striaria 
Agardhiella 
Dictyosiphon 
Turnerelia 
Fudesme 
Futhora 
Castagnea 
Halosaccion 
Leathesia (?) 
Phodomda 
Pdf Pia (?) 
Odonthalia 
Chorda 
Pt /Iota 
Phyllaria 
Dilsea. 
Genera that can in consequence 
of their present distribu- 
tion hardly have been anything but tertiary-atlantic are: 
Sorocarpus 
Scapl/ospora 
Dichospora ngium 
Himanth alia 
Isthmoplea 
Pelvetia 
Halopteris 
Ascophyllum 
Physematoplca 
Halidrys 
Delamarea 
Paccar ia 
Pogotrichum 
Sphaerococcus 
Arthrocladia 
Grinnellia 
Goibia 
Halurus 
Leptonema 
Compsotli amnion 
Halothrix 
Dudresnaya 
Cutleria 
Furcdlaria 
Tilopteris 
Polyides. 
Of course the above lists cannot 
have any claim to be 
reckoned as complete, probably still 
more genera could be 
added to the former, and as to the latter there is always some 
doubt left if not their tertiary home can still have been on the 
north side of the landbridge (cf. the above quotation from 
Keinke), but tlien we must either suppose that they have been 
destroyed by the progress of glaciation on their way to Bering 
Strait or also alter the previous supposition that the flora in the 
old Polar Sea has been a uniform one, a theory that is rather 
