3i8 



SAMUEL W. WILLIS TON 



Pelvis. — Of the pelvis the ilium is not visible in its entirety 

 in any specimen. In the restoration I have borrowed from Broili's 

 figure the outline of the upper part articulating with the sacral 

 ribs. The flat, platelike pubes and ischia are firmly united in the 

 middle, with no opening except the usual obturator foramen ; they 

 are proportionally long. 



Hind legs. — The femur has been well figured by Case. It is 

 rather short and stout, much stouter than in Captorhinus. The 



tibia is unusually stout, and the 

 fibula is much curved; both bones 

 are much shorter than the femur. 

 My original figure of the tarsus 

 was erroneous in several particu- 

 lars, as was suggested by Jaekel. 

 Most of the tarsal bones have been 

 correctly figured by Case. In one 

 specimen (No. 174) I find what I 

 believe to be evidence of two cen- 

 tralia, as in Ophiacodon, though 

 Case figures but one. The phalan ■ 

 geal formula was doubtless 2, 3, 4, 

 5, 4. The first three digits are 

 shown in the figure (Fig. 1). The 

 first digit of both the hand and the 

 foot is relatively large, and its 

 metapodial was capable of but 

 little divarication from the others. 

 The fifth metapodial was but little 

 shorter than the fourth. 

 Parenthetically I may add that I do not at all agree with Good- 

 rich 1 in imputing to the form and position of the fifth toe so much 

 importance in the classification and phylogeny of the reptiles. 

 The divarication and hook shape of the fifth metatarsal have been 

 due, I believe, to modifications of the tarsus and doubtless have 

 arisen homoplastically in various lines of descent. In all primitive 

 reptiles there was a fifth tarsale. As has been amply proved, I 



1 Proc. Royal Soc, LXXXIX (19 16), 261. 



Fig. 7. — Labidosaurus. Outline of 

 skull, from above: pm, premaxilla; 

 n, nasal; m, maxilla; /, lacrimal; 

 p, prefrontal; fr, frontal; pf, post- 

 frontal; po, postorbital; j, jugal; 

 pa, parietal; sq, squamosal; ds, der- 

 mosupraoccipital; pf, parietal fora- 

 men. (Engraving from Water Rep- 

 tiles, p. 22, Fig. 6.) 



