290 Prof. H. G. Seeley on a 



XLTir. — On a new Type of Reptilian Tooth (Ptychocynolou) 

 from the Upper Karroo Beds near Bar.jfiersdor^), Gipe 

 Colony. By H. G. Seeley, F.R.S. 



In 1897 Dr. Kannemeyer discovered and sent to me tlie 

 fragment of a tooth which is now described. He fully 

 appreciated the scientific interest of the fossil, and I have 

 only delayed making his discovery known in hope that the 

 labours and acumen which have added so much to our know- 

 ledge of South-African reptiles might have been rewarded 

 with more complete evidence of the animal. 



The fragment, which is less than an inch and a quarter 

 long, appears to be a portion of a large stout tusk of a new 

 genus of fossil reptiles with canine teeth comparable to the 

 l)icynodont type. In transverse section it measures one inch 

 and a half from back to front and an inch and a quarter from 

 side to side. It was presumably long, for the decrease in 

 transverse measurements towards the fractured extremity is 

 very small. 



This tooth differs from all genera of reptiles hitherto known 

 in having the tooth-substance folded longitudinally into a few 

 large flexures, which are not symmetrical and vary in size, 

 giving rise to an angulated pulp-cavity. The appearance is 

 that of a plastic substance which had become corrugated by 

 compression, and, yielding towards the pulp-cavity, had 

 acquired a complex folded structure. But in the transverse 

 section the microscopic condition of the dentine is normal and 

 leaves no doubt that the folding is a tooth-character of a new 

 type differing fundamentally from that of known Labyrintho- 

 donts. The root of the tooth exposes a five-rayed pulp-cavity. 

 Each ray corresponds to one of the five parallel vertical 

 convex bars or folded flutings which make the external 

 surface of the tooth. This basal extremity is broken and 

 weathered, showing that the tooth has long been separated 

 from the skull. The dense tooth -substance is about two 

 tenths of an inch thick on each of the five bars. These bars 

 are divided from each other by narrow folds directed inward, 

 which vary in depth and size. The walls of these inlets are 

 thin, being less than half the thickness of the intervening 

 tooth-substance. 



Owing to strain in the undulatory movements which have 

 affected these rocks the continuity of the thin walls of the 

 inlets is sometimes broken, giving the pulp-cavity the appear- 

 ance of opening externally. The anterior inlet A (fig. 1) is the 



