These species thus answer to the living _Sequoia sempervirens_; but we can also point to Tertiary representatives of the _S. gigantea_. Their leaves are stiff and sharp-pointed, are thinly set round the branches, and lie forward in the same way: the egg-shaped cones are in some cases similar. There are, however, in the early Tertiary six species, which fill up the gap between _S. sempervirens_ and _S. gigantea_. They are the _S. Couttsiæ_, _S. affinis_, Lesq., _S. imbricata_, Hr., _S. sibirica_, Hr., _S. Heerii_, Lesq., and _S. biformis_, Lesq. Of these, _S. Couttsiæ_, Hr., is the most common and most important species. It has short leaves, lying along the branch, like _S. gigantea_, and small, round cones, like _S. Langsdorfii_ and _sempervirens_. Bovey Tracey in Devonshire has afforded splendid specimens of cones, seeds, and twigs, which have been described in the _Philosophical Transactions_. More lately, Count Saporta has described specimens of cones and twigs from Armissan. Specimens of this species have also been found in the older Tertiary of Greenland, so that it must have had a wide range. It is very like to the American _S. affinis_, Lesq. In the Tertiary there have been found fourteen well-marked species, which thus include representatives of the two living types, _S. sempervirens_ and _S. gigantea_. We can follow this genus still further back. If we go back to the Cretaceous age, we find ten species, of which five occur in the Urgon of the Lower Cretaceous, two in the Middle, and three in the Upper Cretaceous. Among these, the Lower Cretaceous exhibits the two types of the _Sequoia sempervirens_ and _S. gigantea_. To the former the _S. Smithiana_ answers, and to the latter, the _Reichenbachii_, Gein. The _S. Smithiana_ stands indeed uncommonly near the _S. Langsdorfii_, both in the appearance of the leaves on the twigs and in the shape of the cones. These are, however, smaller, and the leaves do not become narrower toward the base. The _S. pectina_, Hr., of the Upper Cretaceous, has its leaves arranged in two rows, and presents a similar appearance. The _S. Reichenbachii_ is a type more distinct from those now living and those in the Tertiary. It has indeed stiff, pointed leaves, lying forward, but they are arcuate, and the cones are smaller. This tree has been known for a long time, and it serves in the Cretaceous as a guiding star, which we can follow from the Urgonian of the Lower Cretaceous up to the Cenomanian. It is known in France, Belgium, Bohemia, Saxony, Greenland, and Spitzbergen (also in Canada and the United States). It has been placed in another genus--Geinitzia--but we can recognize, by the help of the cones, that it belongs to Sequoia. Below this, there is found in Greenland a nearly related species, the _S. ambigua_, Hr., of which the leaves are shorter and broader, and the cones round and somewhat smaller.