328 ME. T. ATTHEY ON ANTHRACOSAUHUS RUSSELLI. 



of the pulp-cavity into both the light and dark dentine ; those 

 passing into the former, after the most beautiful wavy windings, 

 end in the sides of the infolded peripheral band ; those of the 

 latter radiate to the periphery. No granular layer of dentine is 

 seen in this section. 



Fig. 4 is a transverse section a little below the alveolar border, 

 a portion of which is attached to the section. The tooth has at 

 this part been crushed, and parts of the dentine are here and 

 there displaced ; but it can be seen that the full complexity of 

 the tooth is here displayed, and that the cavity is elliptical. 

 The dark dentine of the exterior of the tooth is much less in 

 proportional size than the light. The spindle- shapes of the 

 latter are no longer visible, but are represented by tracts passing 

 in from the dark exterior and folding upon themselves as they 

 pass towards the pulp-cavity, the outline of which is far from 

 distinct, owing to the breakage of the parts around. Into each 

 of these tracts enters, from without, the narrow peripheral band 

 noticed under fig. 3 as being very light-coloured and sinuous. 

 In fig. 4 this narrow band is much more sinuous, and follows 

 the windings or convolutions of the light dentinal tracts to near 

 their extremities, which are frequently continuous with each 

 other ; but the infolded narrow tracts are not so, keeping sepa- 

 rate. The narrow bands are here dark instead of light in colour, 

 and granular. The folded tracts are here and there separated 

 from each other by clear but irregularly shaped spaces, which 

 are parts of the offsets of the pulp-cavity. 



There are, intervening between the commencements of these 

 long winding tracts at the peripheral layer of dentine, others 

 which are very short, rudimentary, and mammillary, projecting 

 into the outer ends of the divisions of the pulp-cavity. These 

 also have a narrow dark band of granular dentine in their inte- 

 rior. The same arrangement occurs in the teeth of Loxomma. 



The dentinal tubes all radiate from the margins of the central 

 pulp-cavity and its ramifications ; most of them pass through the 

 light-coloured dentine of the sinuous tracts, and end in the nar- 

 row dark band running through them ; those, however, which 

 radiate outwards from the ends of the offsets of the pulp-cavity 



