298 ON A MOLAR TOOTH OF ZEUGLODOIf, 



0:^ A Molar Tooth of Zeuglodon from the Tertiary Beds on 

 THE Murray Eiver near Wellington, S.A. 



ByE. B. Sanger, Esq., South Australia, O.M.L.S. N.S. Wales. 

 The tooth and the fragments of a second were found in a bed 

 of yellow calcareous clay, containing specimens of Echinus, 

 Spatangus, Chjpeaster, Pecten, Turritella, Corhis, and Sjwndijlus. 

 The tooth is compressed laterally, and strongly serrated on the 

 anterior and posterior edges of the crown, forming four cusps on 

 one edge, six on the other and one median and terminal. (See 

 figure). The cusps increase in size from the base up, the median 



B 



E. B. Sanger, del, 

 A. Molar tooth of Zeuglodon Harivoodii, nat. size. 

 B. Transverse vertical section through the fangs, nat. size. 

 cusp being the largest. At the junction of the double fang and 

 the crown the tooth suddenly thickens out, thus forming a ridge 

 which runs around the tooth curving up in the middle on both 

 sides in the ''yoke" thus making a sharp line of demarcation 

 between the crown and the fang. The crown is covered with 

 enamel which in one place has broken or peeled off, showing the 

 dentine beneath. The double fang is formed by two pillars 

 connected mesially by a thin isthmus through which the pulp- 

 cavities of the pillars are connected. The two pillars and the 

 crown arching over them form the characteristic ''yoke" from 

 which the name is derived. The half of the tooth of which the 

 edge bears four cusps, and its corresponding pillar or fang is 

 larger and thicker than the other half ; and the pulp-cavity of its 



