ON ANTHEACOSAURUS RUSSELLI. 817 



widest part. That they were of nearly equal size is apparently 

 confirmed by the dimensions of the vomerine tusks. 



Those of the Newsham specimen seem to be quite as large as 

 those of the Scotch specimen ; in both they are about equal in 

 diameter at the base. It is true that Professor Huxley estimates 

 their length in the Scotch specimen to be three inches, while, 

 judging from the fragments, we have calculated that the left 

 tusk in our sj)ecimen could not be less than two inches long ; 

 but how much longer it may have been we cannot determine. 

 It is certain that the two fragments into which it is broken, when 

 taken together, measure upwards of two inches in length ; and 

 it is impossible to say how much the basal portion overlies the 

 upper : moreover the latter is bent, and the apical extremity is 

 wanting. We think, then, that the disparity in the number and 

 size of the teeth and tusks is not sufficient to cause us to doubt 

 the specific identity of the two specimens in question. 



We must now turn to the character of the teeth themselves. 

 In our specimen they have the same irregularly rounded base as 

 those of the Scotch specimen ; and like them they are, towards 

 the apex, a little flattened, giving to the section of the crown an 

 elliptical contour, the long axis being in the direction of the jaw; 

 and on the frontal and dorsal aspects they are slightly carinated. 

 So far the teeth agree ; but Professor Huxley describes the sur- 

 face of those in his specimen as ridged, not grooved, while in 

 ours they may be said to be both grooved and, to some extent, 

 ridged. The base of the teeth, when in a good state of preser- 

 vation, exhibits narrow, shallow grooves, the interspaces being 

 comparatively wide and usually a little prominent, though some- 

 times almost flat. This difference in the two instances is, per- 

 haj)s, of not much importance, and may be accounted for by the 

 peculiar state of preservation of the specimens : we shall shortly 

 endeavour to show that this is the fact ; in the meantime we will 

 say a few words on the internal structure of the teeth. In this 

 respect there is also some slight difierence ; our sections of the 

 teeth and those described by Professor Huxley do not exactly 

 agree. The only difference of any consequence, however, can 

 be explained, Ave think, by supposing that the sections were 



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