354 MESSRS. HANCOCK AND HOWSE 



give off, almost at right angles, small, irregular, branched and 

 anastomosing tubes, which, penetrating the overlying white ena- 

 mel-like matter, abut near to the surface. The white matter 

 also penetrates occasionally into the interior of the tooth, insin- 

 uating itself between the tubes ; but the central portion is usually 

 so exceedingly dense that few traces of it are to be observed. 

 On the upper or concave face of the cutting-margin, however, 

 the dentinal tubes, which are here small and arranged lengthwise 

 in parallel order, lie buried in the white matter that in many in- 

 stances permeates the entire scoop portion. 



The tubular matter, whether at the surface or in the interior, 

 is composed of concentric layers ; and coarse, branched tubules, 

 originating in the medullary channels, penetrate their walls. The 

 whole of the brown tubular matter composing the mass of the 

 tooth is probably dentine, as we have just stated ; or it may be, 

 as stated in the paper already quoted on Climaxodus and Janassa, 

 osteodentine, the small marginal tubes only being dentine ; but 

 the structure of the whole appears to be the same. We feel 

 equally at a loss how to denominate the white matter.* It is 

 minutely granular, but otherwise quite structureless. If we are 

 correct in designating it enamel, then there must be two kinds 

 of enamel ; or what is the transparent film seen on the surface 

 in perfect specimens ? 



When the white coating is worn a little, the extremities of the 

 small dentinal tubes that penetrate it are seen at the surface, 

 and as they wear more readily than the white matter, the whole 

 surface becomes minutely punctured. On the cutting-margin, 

 however, the white matter is usually to some extent minutely 

 gi'ooved longitudinally, in consequence of these superficial tubes 

 of the dentine-like matter running parallel to the surface. 



The minute structure of the tooth as above described is seen 

 to be essentially the same as that of the so-called Climaxodus ; 

 but in the latter the brown dentinal tubular matter of the interior 

 is not so dense, consequently the white matter penetrates more 



* In the paper on CHma-xodus and Janassa this white coating is called "cement." On 

 further examination, however, we find that it has not the character of cement, but is merely 

 granular, and in every respect is similar to the white external layer in Janassa. 



