NO. I 



THE WHITE RHINOCEROS HELLER 



15 



of the two African species. Ceratotherium has 22 thoracico-lumbar 

 vertebras, one less than the number found in Diceros. It is rare to 

 find any variation in number of thoracico-lumbar vertebrae between 

 allied genera, usually discrepancies of this sort are due to the anterior 

 lumbar vertebrae becoming rib-bearing, reducing the number of 

 lumbar, but leaving the whole number of thoracico-lumbar vertebrae 

 the same. The other two genera of rhinoceroses examined, Rhinoce- 

 ros and Dicerorhinus, show 22 or 23 thoracico-lumbar vertebrae, 

 which would indicate that a difference of this sort is not of a very 

 fundamental character. Diceros, however, stands alone in the pos- 

 session of one more thoracico vertebra than any other living species of 

 rhinoceros. The number of rib-bearing vertebrae in Ceratotherium 

 is 18, two less than in Diceros and one less than in Rhinoceros or 

 Dicerorhinus. The caudal vertebrae are apparently less in number in 

 Ceratotherium, but the material examined is not reliable, some of 

 the specimens obviously lacking one or more vertebrae, while others 

 seem to exhibit substitution of parts. The tail of the British Museum 

 specimen shows 16 vertebrae, but one or more anterior ones are 

 obviously wanting. The Paris specimen, however, which has 20 ver- 

 tebrae in the tail is made up near the tip of very irregular bones, which 

 do not show the exact fitting and gradation of a perfect series. Of 

 the four perfectly tailed specimens of Diceros which have been 

 examined at the British Museum three show 22 vertebrae. In the 

 Paris specimen the tail is wanting. From the data supplied by these 

 specimens there is little doubt that Diceros has some several caudal 

 vertebrae more than Ceratotherium. Both species, however, will be 

 found to exhibit some individual variation in the number of caudals 

 due to actual differences in numbers as well as to anchyloses with the 

 sacrum in age. The number of sacral vertebrae is quite variable, 

 the amount of anchyloses in this region depending upon age chiefly, 

 and concerning itself with the caudal vertebrae. 



There are some differences in the shape and size of the third tro- 

 chanter of the femur in the two living African rhinoceroses. In Cera- 

 totherium this process is usually shorter and forms a smaller notch 

 with the great trochanter above it. The upwardly directed angle of 

 the third trochanter is less produced, or shorter, and the entire process 

 is smaller than in Diceros; but in Diceros these trochanter processes 

 are never united to form a closed foramen as occurs in aged specimens 

 of Rhinoceros unicornis. 



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