358 Annals of the SoutJt African Museum. 



and much doubt left as to their relative positions. In describing the 

 specimen Seeley considered that there were 5 toes on each foot, but 

 was doubtful as to the number of phalanges in each toe. He says 

 (p. 363) : "I have no certain evidence of more than 3 phalangeal 

 bones in any digit, but it is possible that one may have had 4." 

 From further study of the specimen he stated, in 1895, that the digital 

 formula of Pareiasaurus appeared to be " I., 3 ; II., 4 ; III., 4 ; IV., 



3 ; v., 3 " ; or 17 phalanges on each foot. As the 1st and 2nd digits 

 are very unlikely to have had more than 2 and 3 phalanges respec- 

 tively — numbers never exceeded in land animals — we may infer that 

 the 2 extra phalanges belong to the 4th toe, and we would thus have 

 Pareiasaurus with the typical formula of primitive reptiles, viz., 2, 3, 

 4, 5, 3. When in 1903 I described the South African Museum 

 specimen of Pareiasaurus 1 was unable to give any definite digital 

 formula, as the phalanges were mostly displaced. Two toes, how- 

 ever, had the phalanges in contact — one with 3 and the other with 



4 phalanges. These I inferred to be the 2nd and 3rd toes, and I 

 thought it likely that the whole formula wovild prove to be similar to 

 that of Procoloplioa. In 1904 Boulenger definitely stated that the 

 formula of the British Museum specimen is 2, 3, 3, 4, 3, but he does 

 not say how the conclusion has been arrived at, and if Seeley was 

 unable to tell even to which foot the different toes belonged, and was 

 not very sure whether any one had 4 phalanges, it is difficult to see 

 how Boulenger obtained his result. The allied reptile Sclerosaurus 

 is rather badly preserved, but the formula appears to be 2, 3, 3, 4, 3, 

 and Pareiasaurus might well have had the same. The evidence 

 derived from Propappus, however, casts some doubts on this formula, 

 as it is very unlikely that these two genera, which are so closely 

 allied, had different phalangeal formulae. Now it can be stated with 

 much certainty that two digits in the pes had more than 3 phalanges. 

 These are the 3rd and 4th. The 1st and 2nd digits there can hardly 

 be any doubt had 2 and 3 phalanges respectively, and the 3rd cannot 

 have had more than 4, while there is a fair amount of evidence in 

 favour of the 4th digit having had 5 phalanges. The specimen 

 affords no evidence of the number of phalanges in the 5th digit. It 

 was probably feebly developed. On the whole, the most likely 

 digital formula for Pareiasaurus and ProjMppus is 2, 3, 4, 5, 3. It 

 certainly cannot be 2, 3, 3, 4, 3 in the latter. 



Dermal x\rmour. 

 The most remarkable characteristic of Propappus, and the most 

 marked feature which distinguishes it from Pareiasaurus, is the great 



