Our illustration, carefully studied, may do more to present to the reader the teeming swarms of the Silurian seas then our word-picture, and it includes many animal forms not mentioned above, more especially the curved and nautilus-like cuttle-fishes, those singular molluscous swimmers by fin or float known to zoologists as violet-snails, winged-snails or pteropods, and carinarias; and which, under various forms, have existed from the Silurian to the present time. The old _Lingulæ_ 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 fragments of wood representing the curious and primitive type of pine-like trees known as _Prototaxites_. These are probably only a small instalment of Silurian land plants, such as a voyager might find floating in the sea on his approach to some unknown shore, which had not yet risen above his horizon. Time and careful search will, no doubt, add largely to our knowledge.