76 THE STORY OP THE EARTH AND MAN. 



Silurian seas tliaii our word picture, and it includes 

 many animal forms not mentioned above, more especi- 

 ally the curved and nautilus-like cuttle-fishes, those 

 singular molluscous swimmers by fin or float known 

 to zoologists as violet-snails, winged-snails or ptero- 

 pods, and carinarias; and which, under various forms, 

 have existed from the Silurian to the present time. 

 The old Lingulce are also there as well as in the 

 Primordial, while the fishes and the land vegetation 

 belong, as far as we yet know, exclusively to the 

 Upper Silurian, and point forward to the succeeding 

 Devonian. We know as yet no Silurian animal that 

 lived on the land or breathed air. But our knowledge 

 of land plants, though very meagre, is important. 

 Without regarding such obscure and uncertain forms 

 as the Eophyton of Sweden, Hooker, Page, and 

 Barrande have noticed, in the Upper Silurian, plants 

 allied to the Lycopods or club-mosses. I have 

 found in the same deposits another group of plants 

 allied to Lycopods and pill-worts (Psilophyton), and 

 remains of wood representing the curious and 

 primitive type of pine-like trees known as Proto- 

 taxites, fragments of the wood of which have been 

 found by Hicks in beds at the base of the Upper 

 Silurian ; while in America, Claypole and Lesquereux 

 have described plants, probably allied to club-mosses, 

 from beds quite as old. A still older plant, possibly 

 allied to the mares'-tails, has been found by Nichol- 

 son in the Skiddaw beds. 



In the Silurian, as in the Cambrian, the head- 

 quarters of animal life were in the sea. Perhaps there 



