THE EOCENE OF EUROPE AND NORTH AMERICA 117 



Fig. 33), is a somewhat more progressive horse, and is similar in its 

 stage of evolution to tlie Eohippus vdlidus of the Rocky Mountain region, 

 which has the simplest fourth superior premolar of any of the American 

 hyracotheres. We note especially the swelling brain case of these little 

 horses (Fig. 33), indicative of a comparatively well-developed cerebrum. 

 This London Clay phase is evidently of the Coryphodon Zone, broadly 

 corresponding with the Wasatch, but possil)ly a sliade older. 



Fortunately our knowledge of the contemporary fish, rei^tile, and bird 

 life is quite extensive. The fishes of the London Clay include rays (Mylio- 

 batis), sharks {Odontaspis, Lamna), sun-fishes (Tetrapterus), and saw- 

 fishes (Pristis). Among the reptiles are marine and freshwater turtles 

 and tortoises {Chelone, Trionyx, Platemys), two species of crocodile, and a 

 sea-snake (Palceophis) of large size. Among the birds are Steganopodes, 

 allies of the pelicans and cormorants; Dasyornis, also, a giant bird pos- 

 sibly allied to Gastoi'tiis, has been discovered.^ 



Of still greater interest is the rich land flora preserved in the Isle of 

 Sheppey deposits near the mouth of the Thames." This gives by far the 

 best picture we have both of the environment and temperature of the 

 most remote period of the horse. We find palms {Nipa, Sabal, Chamoe- 

 rops), conifers (Sequoia, Pinus, CaUitris, now of Africa), the plantain 

 (Musa), now confined to eastern Asia, the eucalyptus (Eucalyptus), now 

 characteristic of Australia, the tupelo (Nyssa) now exclusively North 

 American. There are also oaks, laurels, sweet gums (Liquidambar) , mag- 

 nolias, almonds (Amygdalus), and soapberries (Sapindus), altogether a 

 flora south temperate rather than subtropical. 



Characteristic Upper Ypresian Formations. — While the Lower 



Mammals Ypresian is in the Coryphodon Zone and corresponds 



in age with the American Wasatch and Lower Wind 



Dichobunids River depositions or close of the Lower Eocene, the 



(Artiodactyls) Upper Ypresian lacks Coryphodon and contains a more 



Hyracotheres recent fauna which, as Deperet observes, approximates 



(Horses) it more closely to the Middle Eocene. It thus perhaps 



Lophiodonts corresponds to the Upper Huerfano and base of the 



Inscctivores Bridger Formations of the Rocky Mountain region. The 



(?) Lemurs typical stage is locally known as the Sables a Teredina 



(?) Mesonychids personata, especially exposed in northern France near 



Epernay, at Chavot (22), a marine formation, at Ay 



(22), and at Cuis. These are the Sables ageiens of Lemoine. 



These Teredo sands contain the faune ageienne of Lemoine, which partly 



' Geikie, A., Text-Book of Geology, 1893, p. 973; and Boyd Dawkins. Early Man in 

 Britain, 1880, p. 19. 



* J. S. Gardner's British Eocene Flora (Paleont. Soc, p. 12), as (luoted by A. Geikie, 1893, 

 p. 973. 



