Vol. II, Pt. I] VAN DENBURGH— GALAPAGOS TORTOISES 291 



that can be said for it is that it seems the only solution of a 

 most difficult problem, and must be regarded as a necessary evil. 

 Although sharp lines cannot be drawn between the various 

 races, I shall use binomials in referring to them, since I believe 

 nothing is to be gained by a more cumbersome nomenclature 

 when dealing with such insular forms. 



4. Individual Variation. — In the shape of the carapace this 

 variation is very considerable, as is shown by the charts of 

 measurements. There is also much variation in the size attained 

 by different specimens. Some very old individuals are much 

 smaller than younger ones of the same races. The horny plates 

 are remarkably constant in number and shape, but certain indi- 

 vidual variations occur. The type of T. microphyes has the 

 anterior two marginals of each side merged into single plates. 

 One specimen of Testudo vicina (No. 8254) from Vilamil has 

 an intergular plate. Another (No. 8196) has a single light- 

 yellow ray on one second costal, and an extra plate in the front 

 part of the plastron. Van Lidth de Jeude has figured a speci- 

 men of T. ephippium in which the pectorals do not reach the 

 midline. This variation seems not very rare in this race. I 

 have noted it in Nos. 8321 and 8333 ; and Nos. 8332 and 8367 

 have the left pectorals not extending to the midline, although 

 those of the right side reach it. In this Duncan Island race 

 also No. 8375 has five left costals, No. 8326 has five right cos- 

 tals, and No. 8361 has five right costals, and also has the third 

 vertebral divided into three irregular portions. In No. 8265 

 {Testudo gi'mtheri) the pectorals are divided longitudinally. 



The Soft Parts. — These also vary with age, with sex, indi- 

 vidually, and with race. The young have proportionally shorter 

 necks, limbs, and tails than the adults; and the adult females 

 have these parts proportionally shorter than the adult males. 

 In the saddle-backed races these parts are longer than in the 

 dome-shaped races. Both sexes of the saddle-backed races 

 usually have more or less yellow on the lower jaw and throat. 

 This coloration appears also in some of the males of T. gUn- 

 theri, and is found also in the James Island race. The non- 

 saddle-backed forms, the Tagus Cove race, and at least the 

 females of the Chatham race are entirely blackish brown. 



