part 4] THE E LEPRAS- ANTIQU US BED OF CLACI'ON-ON-SEA. 617 



eye they look more slender in their proportions than those of 

 Oervus elapkus ; but the difference in the length-circumference 

 index is not so great as one would expect. Two metatarsi of 

 C. browni give indices of 27*4 and 29 - 6, as compared with two of 

 O. elaphus which give indices of 29"9 and 30 - 3. 



The bones of G. elaphus from Clacton are, for the greater part, 

 smaller than those of a recent skeleton from the Caucasus, in 

 the British Museum (Natural History), marked 689^, of which 

 measurements are given in the accompanying table (p. 616). The 

 chief difference is in the width, which is often 15, or even 20, per 

 cent, less in the case of the Clacton bones ; the difference in length 

 is less considerable. The measurements of a C clama, also in the 

 British Museum (Natural History), are likewise tabulated for 

 comparison with the bones of C. browni. 



The Rhinoceros remains fall into two groups, massive and 

 slender ; and, after careful comparison of the upper molars at the 

 Natural History Museum, Dr. C. W. Andrews and Mr. Martin 

 Hinton came to the conclusion that two species were represented 

 here: namely, Rh. megarhinus de Christol (=Rh. leptorhiniis 

 Cuvier) ; and Rh. hemitcechus Falconer ( — Rh. leptorhiniis Owen). 

 Some French and other authorities, however, consider that these 

 two are one species, for which they use the name of Rh. merchii. 

 Although the two species are very closely related, there do seem to 

 be differences of character, particularly in the upper molars, 

 associated with differences of size, the Rh. megarhinus being the 

 massive form and the Rh. hemitcechus the slender. It seems to 

 me probable that we may be dealing with an evolutionary change. 



It might be urged that the differences between Rh. megarhinus 

 and Rh. hemitcechus might well be those of sex in the same 

 species ; but, as Mr. Hinton points out, their time-range is not 

 the same, the former appearing earlier (in the Forest Bed), and 

 also disappearing earlier, than the latter. 



The comparative weight of the limb-bones is well illustrated 

 by the radius, the massive Rhinoceratan radius having a circum- 

 ference of 160 mm., while two examples of the slender form 

 measure 126 mm. each. Five specimens of the radius in my 

 collection from the Lea-Valley Arctic deposits, where Rhinoceros 

 antiqiiitatis alone is represented, give corresponding measurements 

 of 186, 166, 161, 160, and 154 mm. respectively. The depth, 

 from above downwards, of the symphysis of the lower jaw of the 

 two Clacton forms is 58 and 35 5 mm. respectively. 



Attention has been drawn to differences in the enamel of the 

 molars of Rh. megarhinus and Rh. hemitcechus. Dr. Andrews 

 doubts whether much reliance can be placed upon this, and it is 

 certainly very difficult to find an} r difference in the lower molars, 

 assuming that the difference in size also represents the specific 

 difference. But, in my specimens of the upper molars, there 

 certainly is a difference, although it ma} r be no more than acci- 

 dental. In Rh, hemitcechus the enamel appears to the eye more 



2 t 2 



