198 Report S.A.A. Advancement of Science. 



parts of the colony, and also the western areas, modifications begin to 

 be introduced, suggesting transitions to other well recognized sub- 

 groups. Thus, from the Hex River, Worcester District, are to be 

 obtained variations altogether intermediate between tentoria and 

 trimeni, the latter sub-group having its headquarters further north in 

 Namaqualand. These specimens already show the breaking-up of 

 the black, central band of the plastron into rays, and the beginnings 

 of a more definite arrangement of the yellow rays on the shields of 

 the carapace, such as is characteristic of trimeni and others, 



Fine examples of tentoria occur in the District of Beaufort 

 West, which borders on the districts whence verreauxii are obtained, 

 and in nearly all their characters they are transitional in the direction 

 of verreauxii. Tracing all the individual variations in detail, com- 

 paring them on the one hand with typical tentoria, and on the other 

 with typical verreauxii, one becomes deeply impressed with their 

 intermediate nature. It would be scarcely possible to obtain better 

 instances of gradational types than those presented by tentoria and 

 trimeni on the one hand, and tentoria and verreauxii on the other, 

 and, as shown in the next section, trimeni and verreauxii differ but 

 little from one another. 



d. Testudo verreauxii, Smith, 1839. 



The forms which I include under this species present a great 

 variety of characters, and several distinct species have already 

 been established upon single individuals which unquestionably belong 

 here. Fortunately, for the present study, a large number of speci- 

 mens, about 150, are available, largely obtained from one locality, 

 namely, the District of Hanover. This large collection I owe to the 

 kindness of Mr. S. C. Cronwright Schreiner, M.L.A. 



In very many of its characters verreauxii is intermediate between 

 tentoria and oculifera. It is sufficient to turn to the discussion on the 

 individual characters to see how frequently members of the sub- 

 group are mtrodliced to establish the transition from the extreme 

 condition of tentoria to the opposite extreme in oculifera. The 

 accessory femoral and caudal shields reach their maximum develop- 

 ment in this species, but all the other characters are transitional. As 

 regards the details of the coloration, scarcely any two specimens are 

 alike, and almost any individual, if considered alone, could be made 

 the type of a species. It is only where one can compare a large 

 number side by side that the extreme lack of fixity of pattern 

 becomes manifest. 



In his paper. Siebenrock distinguishes this species by having the 

 first costal greater than the fourth, and by having alternately yellow 

 and liver red rays on the dorsal shields. The red rays he considers 

 as the most distinguishing feature, as such do not occur in any other 

 species of the geomeirica-gxoup. The seven specimens examined by 

 Siebenrock are from Great Namaqualand and German South-West 

 Africa, while Smith's original specimens came from near the sources 

 of the Orange River. The type of coloration described by Sieben- 

 rock is not met with on anv of the specimens studied by me, all of 



