294 Prof. H. G. Seeley. Researches on the Structure, [June 21, 



placed by a successicmal series, but no known specimen of any genus 

 shows such replacement. 



The skull of Cynognathus platyceps was obtained by Dr. Kannemeyr 

 at Wonclerboom. It is a small species distinct from Cynognathus 

 crateronotns. The skull has lost the extremity of the snout. It is 

 remarkable for its depression. The teeth, however, are similar to 

 those of the larger species ; they have five denticles. The composite 

 structure of the lower jaw is well shown, and the dentary bone be- 

 hind the angle of the jaw retreats so as to expose the elements which 

 form the articulation. 



The occipital plate of a large Theriodont skull from Lady Frere is 

 described, which shows a circular foramen magnum, and the perfectly 

 preserved occipital condyles which are not quite so completely 

 separated as in Mammals, having only a median groove between them 

 on the ventral surface. 



Another fragment of a skull preserved in the Albany Museum has 

 only the pre-orbital portion preserved, and is remarkable for the 

 small size of its incisor teeth, widely separated from each other, and 

 for having two canine teeth parallel to each other. On both sides the 

 crowns are imperfectly preserved. The molar teeth are on the type 

 of Cynognathus, with a principal cusp flanked back and front by a 

 small cusp, with a smaller accessory posterior cusp in the four 

 hindermost teeth. As in all species of the genus the manclibular 

 symphysis is long, oblique, and completely obliterated. There is a 

 large pit with sharp margin, in the median line in front of the orbits, 

 which may be a generic difference from Cynognathus, since it occurs in 

 the area in which other specimens show indications of a thin supra- 

 nasal ossification flanked by a pair of small hemispherical concavities. 

 It is indicated as G. leptorliinus. 



Tribolodon Frerensis is the name given to a dentary bone with few 

 three-pronged teeth widely separated from each other standing high 

 above the jaw. With this jaw is associated a femur which shows the 

 transverse development of the great trochanter as strongly developed 

 at the proximal end of the bone as in Ichthyosaurus, so that the 

 trochanter minor of Mammals only represents that of Theriodonts in 

 miniature, the trochanter being more developed than in Saurischia or 

 any other reptiles. With it is associated a right tibia which is some- 

 what curved and nearly as long as the femur. 



These Cynodont remains have given no certain evidence of the ex- 

 tremities of the limbs ; but with this exception they make known the 

 entire skeleton for the first time in an African Theriodont, furnishing 

 data for comparison with Mammals and Reptiles in every part of the 

 skeleton preserved. 



