150 



DR. R. BROOM ON THE 



The most primitive known tarsus of the lizard-hke group is 

 that of Broomia j)ef2)lexay^idjiion. Though tlie top of tlie skull of 

 this animal is unknown, almost all the rest of the structure is 

 known, and fortunately the tarsus is almost perfectly preserved. 

 As in the large mnjority of early reptiles, there are two lai'ge 

 proximal elements. There are five distal tarsals and two other 

 small elements. The two proximal elements have the usual 

 foramen between them, a,nd are doubtless the fibulare and inter- 

 medium. The two small elements are regarded by Watson as 

 the lirst and second centralis,. I regard the inner one as the 

 imperfectly ossified tibiale. The distal end of the tibia as found 

 is in a position to articulate with what I regard as the cartila- 

 ginous position of the tibiale. Watson, in his restoration, shifts 

 the tibia to make it articulate with the intermedium, which he 

 regards as the fused intermedium and tibiale. If v/e articulate 

 the tibia as Watson has done, the three first digits seem 

 practically without any proximal support — a condition which 



Text-jBgure 13. 



Text-fig-ure 14. 



Text-figure fS. 



Text-fig. 13.— Riglit tarsus and metatarsus of JPaleeohatteria longicandata Credner. 

 A primitive Permian reptile of doubtful affinity. Regarded by Williston, 

 Watson, and others as a Theropsidau : by the \vriter and others as an early 

 Sauropsidau. After Jaekel. 



A cartilaginous tibiale was probably present. 



Text-fig. 14. — Right tarsus and metatarsus of IILrosaurus nordens'kjoldi Hulke. 

 A Triassic Ichthj'osaur. After Wiman. 



Text-fig. 15. — Right tarsus and metatarsus of Stereosternum tumidiuii Cope. 

 A Lower Permian Mesosaurian. After M'Gregor. 



seems very improbaWe. The second small element is doubtless, as 

 Watson holds, a centrale. I give a figiue of the tarsus as found, 

 as restored by Watson, and as I am inclined to restore it (text- 

 figs. 16-18). 



There is another primitive reptile which one wishes one knew 

 more about. I refer to Pcdceohatteria lovgiccvadata Credner. 

 Though first described over thiity years ago, and apparently 

 known by very satisfactory and nearly complete skeletons, we are 

 still in much doubt about the animal and its affinities. For many 

 years it was believed by every one to be a primitive two-arched 



