GYMNOSPERMtE. 19 



region except the Australian, is divided into three sections. It is recorded as fossil from 

 Aix, Haring, and the amber-beds of Prussia ; but the small size of the fragments known, 

 and the absence of fruit, render the determinations somewhat doubtful. The same 

 species is supposed by Saporta to have persisted in Provence to the present day. A 

 few fragments from the Upper Cretaceous of Greenland are known ; and /. rigida, from the 

 Tertiary of Spitzbergen, is based on an indistinct mutilated fragment, three quarters of 

 an inch long. Its comparative rarity in the Arctic fossil floras is remarkable. 



The foliage of Thuya is imbricated like that of Libocedrus but is less symmetric, and 

 the cones are small, leathery, oblong, or oval, and of six to ten valvate unequal scales, 

 persistent and gaping after shedding seed. The species are divided into five sections^ 

 and some attain gigantic dimensions. They inhabit principally North America, Japan, 

 and China. No remains are known below the Tongrian beds of Armissan, where they 

 are rare. Saporta, who has described them, believes the species T. europoea to be 

 intermediate between Thuyopsis dolobrata and T. horealis, and from the identity of the 

 foliage considers it the same as that which is included in the amber-beds in the north. 

 Thuya, which formed vast forests on the Baltic during the latest Miocene, becomes 

 plentiful to the south in the Pliocene deposits of Tuscany and Marseilles. T. europoea 

 is claimed by Heer as an Arctic fossil on the strength of a terminal shoot, only three 

 quarters of an inch long, from Atanekerdluk ; and other species, Thuyites Mireiiswardi, T. 

 Meriani, and T. Pfaffii, are based upon no better material. Bowerbank supposed his 

 Cupressinites crassus from Sheppey to be near Thuya orientalis. The widespread conifer, 

 formerly known as Chamcecyp}aris Hardtii, of European Eocenes, is now recognised to be 

 a Sequoia. 



The three remaining genera are represented in the British Eocenes. 



Genus — Callitris. 



Elowers monoecious or rarely dioecious, terminal. Cone globose or conical ; valves 

 three to six, rarely eight, even, or every alternate one larger, woody, persistent, dehiscent 

 when ripe ; seeds numerous, oblong, crustaceous, two to three-winged. Leaves scale- 

 like and imbricated, or rarely acicular on the sterile branches. 



The genus, as it now exists, is subdivided into four sub-genera, of which only 

 certain characters need here be referred to. 



1. Pachylepis, or Widdrinytonia, distinguished by thick woody cones, with four sub- 

 equal valves. Confined to South Africa and Madagascar. Species 3. 



2. Tetraclinis, or true Callitris, cones with four valves. Confined to North 

 Africa. Species 1. 



