yol. 55.] from rk^tic beds neae bridgend. 95 



Discussion. 



Prof. Seelet said that he had examined ail the linowii remains of 

 fossil reptiles from the Trias, and had been impressed by their diversity 

 in the limb-bones and pelvis. This led him to a detailed examination 

 of the teeth, which among the Megalosanroid forms show two con- 

 ditions, defined by crenulation of the margins. First, in Dimodo- 

 saurus, Thecodontosaurus^ and Picrodon the creuulations had a 

 serrated character, with the denticles not at right angles to the 

 margin of the tooth but more or less directed upward, differing in 

 degree, as well as in the form of the crown. Secondly, in Palceo- 

 sauras, Zanclodon, Avalonia, and Euskelosaurus, the denticles more or 

 less resembled Meyalosaurus in being at right angles to the cutting- 

 margin of the tooth ; but in each genus they differ in shape and size, 

 and the character of the crown is different. These modifications, 

 which were once regarded as indicating species of Mer/alosaurus, are 

 known to be associated with various types of skeleton, no one of 

 Avhich has much in common with that genus. When it was pro- 

 posed to refer Mr. Newton's fossil to Zanclodon, there was the 

 difficulty that no dentary bone of that genus is known. The 

 reference is therefore hypothetical. A tooth of Zanclodon had been 

 figured, but it shows striking differences from the teeth in this jaw 

 from South Wales. It is highly probable that the maxillary bone 

 with teeth, named Teratosaurus, may be the skull of Zanclodon, but 

 the inflated teeth of that genus are unlike the impressions from 

 Mr. Newton's specimens. He found no ground for placing this 

 fossil with Zanclodon, which is an unknown type so far as its jaw is 

 concerned. The resemblance, however, is remarkably close with the 

 tooth of Avalonia, and in no other genus was he aware of comparable 

 generic characters. Moreover the femur and other bones of Ava- 

 Ionia are in the British Museum, and the femur and corresponding 

 bones of Zanclodon are in the lioyal Museum at Stuttgart ; and 

 comparison shows that the differences between them are generic. 

 The femur differs in proportions, in depth of the distal end, in 

 position of the lateral trochanter, and in form of the proximal end. 

 Avalonia and Zanclodon were very distinct genera. He approxi- 

 mated the South Wales fossil to the British genus Avalonia. On 

 whichever side the weight of evidence in interpretation is found to 

 incline, he congratulated the Author on having made a beautiful 

 addition to our knowledge of the Zanclodontidae. 



Mr. H. B. Woodward said that, in the opinion of Mr. Strahan 

 (who regretted his inability to be present), the horizon of this fossil 

 might eventually prove to be either Ehaetic or Upper Keuper. The 

 ground was still under examination by Mr. Tiddeman. It was, 

 however, a matter of no great importance whether these passage-beds 

 were called Hhaetic or Keuper. Near Wedmore, in Somerset, where 

 similar Saurian remains had been found, there were sandy strata, 

 with Fullastra arenicola, beneath the black Avicula con^orto-shales. 

 The passage-beds, in the areas mentioned, were most closely allied 

 to the lihaetic formation. 



