222 



KNOWLEDGE. 



[October 1, 18§4. 



by an imperfect skull without the teeth, and may prove to 

 be identical with one of the foreign genera. 



Passing on to the hoofed order, one of the most in- 

 teresting of the even-toed section is the Pichodon of the 

 Hordwell and Headou beds, as being the only early British 

 ungulate hanng the upper molar teeth with the four 

 crescentic columns characterizing the true ruminants, to 

 the ancestors of which group it was probably more or less 

 closely allied. Connecting these early ruminant-like forms 

 with the ancestors of the pigs is the Hi/opot(n»iis of the 

 Hempsted beds, in which the upper molars were of the 

 same general type as those of the auoplothere (represented 

 in figure A of our illustration), although the whole form of 

 the creature was more pig-like, the skull being long and 

 narrow, with large tusks, separated by an interval both 

 from the incisor teeth in front and the premolars behind. 

 The Hyopotamus was doubtless a four-toed animal like the 

 hippopotamus, but an apparently allied form from the 

 Headon beds takes its name of Diiiltqius from the reduction 

 of the toes to two in each limb. In the allied Anthni- 

 cot/uriuiii, of both the Hempsted and Headon beds, the 

 molars lose to a great extent the crescentic structure of 

 those of the Hijopntamus ; and in the gigantic Klotherium 

 from Hempsted, and the smaller CluFntpntaiiim of the 

 Bembridge series, we come to ungulates having tubercular 

 molars of the same general type as those of the pigs, 

 although in the upper jaw they retain the five-columned 

 arrangement characterizing the Hyopotamus, and have 

 much squarer crowns than those of the pigs. There can, 

 however, be little doubt that in this group we are very 

 close to the ancestral stock from which the modern pigs 

 and ruminants have alike originated. 



On the other hand, the anoplotheres {Anoplotherium), 

 which occur in the lower OHgocene of the Isle of Wight, 

 and the upper molars of which are shown in figure A of the 



L'jipcT cheek-teeth of ui) AiiojilothoiT, (B) I'ahcotliere, and 

 (C) Cori/phodoii. A is from the right, while B and (' are from the 

 left side. 



accompanying illustration, belong to what is called an 

 inadaptive type — that is, one which has died out without 

 leaving descendants. These long-tailed animals, some of 

 which reached the dimensions of an average-sized mule, 

 were remarkable for the circumstance that the teeth 



formed a continuous series round the jaws, without any 

 interruption by large tusks ; and they were further 

 peculiar among the group to which they belong in that in 

 some cases there were three toes to each foot, although in 

 others they conformed to the more normal type in having 

 but two. In these animals the premolar teeth (two of 

 which are shown on the right side of the figure) were 

 only slightly compressed, but the nearly allied small and 

 dehcately built siphodons take their name from the 

 extreme compression and secant form of the teeth in 

 question, in which respect they recall the modern chevro- 

 tains, or mouse-deer. Whether the xiphodons are really 

 British is not quite clear, although a skull from the red 

 crag, evidently derived from an older structure, has been 

 assigned to them. The large size of the " tear-pit," or 

 lachrymal fossa in front of the eye, has suggested for 

 another member of this group, having teeth of the ano- 

 plothere type, the name of Dacnjthcrhim, the English 

 representative of the genus having been originally 

 described from the Hordwell and Headon beds imder 

 the name of IHchohuiu. 



This completes our list of the even-toed ungulates, and 

 we proceed to notice the few early Tertiary British repre- 

 sentatives of the odd-toed group, or those in which the toe 

 corresponding to the human middle finger is symmetrical 

 in itself and larger than either of the others. To this 

 group belong the well-known palteotheres (Paheothenum), 

 so abundant in the gypsum of the Paris basin and more 

 sparingly represented in the Headon and Bembridge beds 

 of Hampshire and the Isle of Wight. The structiire of the 

 cheek-teeth of a medium-sized representative of this genus 

 is exhibited in figure B of the illustration ; and in general 

 form these animals somewhat resembled tapirs, although 

 the neck was relatively longer, and there were but three 

 toes to each foot. It was long considered that the 

 palfeotheres were on the ancestral line of the horse, but 

 this view is now discarded, and they are considered, like 

 the anoplotheres, to represent an inadaptive type. A 

 much smaller animal described as Anchilophus, of which 

 teeth have been found in the Bembridge limestone, is, 

 however, either very close to, or actually on the ancestral 

 line in question. Its upper molar teeth are not very 

 unlike those of the palseotheres, but have the oblique 

 cross-crests, narrower, less inclined, and separated by a 

 more open valley. Although very common in the middle 

 and lower Eocene beds of the Continent, the large genus 

 of odd-toed ungulates known as LiqMoihm. are represented 

 in Britain only by a single species from the Bracklesham 

 beds. While their teeth are of the same general type as 

 those of the palseotheres and Anchilophus, the upper molars 

 differ in having the outer wd^ll formed by sub-conical 

 columns instead of flattened lobes, thereby resembling the 

 corresponding teeth of the modern tapirs. Although most, 

 if not all of these lophiodons died out without giving origin 

 to any posterity, the case is very difl'erent with the nearly 

 allied little Hyrarotherium, originally described upon the 

 evidence of an imperfect skull from the London clay at 

 Heme Bay, since this genus is one of the earliest to which 

 the ancestry of the horse can be traced. Thanks to the 

 perfect preservation of specimens discovered in the I'nited 

 States, where they were long known under a totally 

 difl'erent name, we now know that the hyracothere was a 

 small four-toed animal, intimately connected with a still 

 earlier five-toed type, while superiorly it leads on to the 

 Anchilophus and certain allied Miocene continental forms, 

 and thus to the modern horse. The hyracothere received 

 its name from an idea that it was related to the existing 

 hyrax ; and it is a curious comment on the early history 

 of paleontology to notice that the lower teeth of a second 



