MR. T. ATTHEY OX AXTHRACOSAURUS RT7SSELLI. 327 



ridges corresponding to the ends of the long diameter; these 

 ridges show the position of the two cutting-edges of the tooth. 

 The dentine pervades the whole area within the enamel, a 

 thickish layer of which encloses the dentine. It does not ap- 

 pear that this part of the tooth has undergone any flattening or 

 other injury. 



Fig. 2 is a transverse section a little below fig. 1 and just 

 below the top of the pulp-cavity. The outlines of the tooth 

 and of the pulp-cavity are oval, that of the former broadly so. 

 No coating of enamel is visible, except at one part, where a por- 

 tion of matrix is adherent to the tooth; a stellate appearance, 

 which strikes the eye at once, arises from the arrangement of 

 fifteen fusiform bodies of light-coloured dentine around the 

 pulp-cavity, radiating from it to the circumference ; the internal 

 apices project slightly into the pulp-cavity and give to its out- 

 line an undulating appearance ; their external and more pointed 

 apices reach quite to the circumference of the tooth, where a 

 narrow peripheral band passes from the outer margin of the 

 tooth directly into each of them, extending for a short distance 

 towards the pulp-cavity. The dentinal tubes of the fusiform 

 bodies all pass into this narrow infolded band, which is dark- 

 coloured, not light as in Loxomma. The light-coloured fusiform 

 bodies appear as if imbedded in dentine of a dark colour, which 

 is owing to the tubules of it being black ; and this dark dentine 

 is broadest at the periphery of the tooth, in each interval be- 

 tween the spindles. The dentinal tubes in this dark part pass 

 from its middle, radiating outwards towards the periphery of the 

 tooth. 



Fig. 3 is a transverse section a little below fig. 2, but still 

 above the termination of the radiations of the pulp-cavity. Its 

 form is more elliptical than that of the former sections; the same 

 radiating fusiform bodies of light-coloured dentine, but of a 

 larger size, are seen, encroaching upon the external darker den- 

 tine ; the narrow infolded peripheral band runs inwards here 

 for two-thirds of the length of the light-coloured spindles ; it is 

 therefore longer, more distinct, and very sinuous. 



The dentinal tubes radiate as before from the whole margin 



