108 



they vary a little as to size, showing that the teeth of the Glyptodon are 

 much more compressed than those of the Megatherium ; hut the teeth 

 differ more materially in their intimate structure, which corresponds with 

 that of the teeth of the existing Armadillos. The main constituent of the 

 tooth, or the dentine, consists of fine calcigerous tubuli, radiating with a 

 pretty straight course from the medullary cavity ; the dentine is surrounded 

 by a very thin layer of cementum ; and the pulp-cavity, at the upper part 

 of the tooth, is consolidated by the ossified remains of the pulp, which is 

 harder than the surrounding dentine, and forms a projecting ridge 

 on the grinding surface. The teeth of the Glyptodon, however, differ 

 in a marked degree from those of all the known species of Armadillo, 

 in being traversed, through the whole length of both their outer and 

 inner sides, by two broad and deep angular grooves, each extending 

 from the opposite sides about one-third across the transverse diameter 

 of the tooth, so as to divide the grinding surface into three portions, 

 joined together by the contracted isthmus interposed between the oppo- 

 site grooves. Of these portions the posterior one is broader than the 

 other two. The sockets present longitudinal angular ridges, corre- 

 sponding to these channels or flutings *, and prove that they were con- 

 tinued through the whole length of the tooth ; this is slightly curved, 

 and the concavity is turned inwards in the teeth of the lower jaw, as in 

 the Toxodon. Presented by Sir Woodbine Parish, K.H, 



517- A fragment of the anterior part of the left ramus of the lower jaw, in- 

 cluding portions of the sockets of the four anterior teeth ; the first is 

 small and simple, and is situated close to the anterior termination of the 



* The generic name of the present extinct South American quadruped relates to the fluted sculp- 

 turing of the tooth, yXiKjciw, si ulpo, olovs, dens. 



Since this name was proposed in Sir Woodbine Parish's account of Buenos Ayres, and in the Pro- 

 ceedings of the Geological Society for March 1839, the discovery of bones and armour of the Glyp- 

 todon, under the name of Hoplophorus, by M. Lund, in the caverns of the valley of the Rio des 

 Velhas, Brazil, has been announced in a letter from that gentleman to M. Audouin, published in the 

 Comptes Rendus, Avril 15th, 1839. Prof. D' Alton of Halle subsequently brought the subject of the 

 Glyptodon before the Meeting of the German Physicians and Naturalists at Erlangen, September 

 1839, and has proposed for it the name of Pachypus. 



