318 MESSRS. HANCOCK AND ATTHEY 



made from different parts of the tootli. In Ptero2)lcix the pulp- 

 cavity, near the root of the tooth, is radiated, as it is in Antlira- 

 cosaurus; a Httle nearer the base the radial spaces are wider, a 

 Httle further up they are contracted, and still higher up they are 

 contracted more, and ultimately they are lost, and the cylindri- 

 cal form of the pulp-cavity established. We may therefore pre- 

 sume that the sections described by Professor Huxley were made 

 near to the base of the tooth in A^ithracosawnis, and consequently 

 the radial form of the pulp-cavity was strongly developed. Our 

 sections are from higher up the tooth, and the result is, that 

 the radiation of this cavity is very imperfect and in part oblite- 

 rated. In other respects the structure appears to agree with 

 Professor Huxley's description ; but this observation applies 

 only to the general arrangement of the parts ; for, as the learned 

 Professor remarks, "the details could only be made intelligible 

 by elaborate figures," and such were not given. 



In Mr. Atthey's collection there is a portion of a right man- 

 dible which was obtained at Newsham, and which we originally 

 thought belonged to Pterojdax, but which we now have no doubt 

 belongs to Antliracosaurus. The surface -sculpture of the bone, 

 the general form, character, and internal structure of the teeth 

 demonstrate this since we have become acquainted with these 

 features in that genus. 



The fragment, which is upwards of 2|- inches long, 1^ inch 

 wide behind, and f ths of an inch wide in front, is the anterior 

 portion of the right mandible ; it has attached to it five teeth ; 

 in front it is perfect ; the posterior portion is broken away close 

 to the fifth tooth, which, though much injured, appears to be 

 about half an inch long. The three next in advance are not 

 quite so long, and are separated from the fifth and from each 

 other by considerable spaces, and from the tooth in front by a 

 space fths of an inch in length. This frontal tooth, which is 

 perfect, is half an inch long and -roths of an inch wide at the 

 base ; it is placed a little way from the extremity, where there 

 is a depression, but whether for the reception of the base of a 

 tooth cannot be determined. The surface of the teeth is ridged, 

 particularly towards the base, agreeing in this respect with those 



