202 Report S.A.A. Advancement of Science. 



of the carapace, there is nothing to distinguish it from an ordinary 

 member of the verreaiixii sub-group. Siebenrock (p. 308) has also 

 expressed the opinion that, judging from Boulenger's figure and 

 description, the species is much nearer verreauxii than tentoria. 



j. Testudo boettgeri, Siebenrock, 1904. 



This is a species lately founded by Siebenrock for a single shell 

 from Greater Namaqualand, Boettger having previously determined 

 it as T. smithii. The latter considered the habit of the shell to ally 

 it with smithii, but the colour of the upper surface to be different ; 

 Siebenrock holds that the coloration is most nearly allied to that of 

 trimeni, only there is wanting the small, yellow spot at the junction 

 of adjacent costal plates shown in Boulenger's figure of trimeni. 

 According to Siebenrock also, its habit brings it nearest to s^nithii, 

 but the upper surface of the shell is flatter, particularly in the 

 vertebral region ; the chief difference, however, lies in the comparative 

 sizes of the plastral shields, the gulars being much longer than in 

 smitliii and verreauxii. The relative proportions between the free 

 portion of the margin of the carapace and that united with the bridge 

 are also different from usual. The black spots on the areola employed 

 by Siebenrock as an important diagnostic feature for this and other 

 species are very inconstant in specimens of verreauxii from the same 

 locality. 



From all this it is evident that boettgeri has no definite charac- 

 teristics, constant in nature, which serve to separate it from the 

 variable sub-group which includes trimeni, smithii, iiskii, and 

 verreauxii ; moreover, the shell was obtained from the area whence 

 trimeni was first obtained. 



2. DISCUSSION. 



a. Number of Species Represented. 



The foregoing account fully establishes that we have in the 

 geometrica-group of tortoises a remarkable series of allied forms, 

 including a certain number which may be considered as extreme types, 

 with fairly fixed characteristics, connected by a large number of 

 intermediate forms with variable characteristics. It must be acknow- 

 ledged that if the members of the extreme types only were known 

 there would be no hesitancy in according them full specific rank. 

 Ever since their discovery no one has questioned the true specific 

 value of the forms embraced under geometrica, oculifera, tentoria, 

 and verreauxii, and it is only the acquisition of a large number of 

 related individuals which renders their standing doubtful. As regards 

 the other species, I am of opinion, now the degree of variation 

 is better known, that reliable, distinguishable characters are not 

 available ; founded, as they were, mostly upon single specimens, 

 it was impossible at the time to determine the true taxonomic value 

 of the characters presented. The conclusion may be stated in another 



