XCvi PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



which the probable object is unknown. On the basis of these 

 distinctive characters, particularly on the flexibility of the tail, M. 

 Nodot considers himself justified in establishing a new genus, to 

 which he has given the name Schistopleurum (from g^igtos, cut, 

 7rAevpoy, side), in reference to the segmentation, by which character 

 it is approximated nearer to the genus Armadillo than to the Glyp- 

 todon. I do not think it necessary to follow M. Nodot into minuter 

 details, from the consideration of which he has established three 

 species of his new genus, S. typus, S. gemmatum, S. tuberculatum, 

 and added to the genus Glyptodon five, viz. G. subelevatus, G. ele- 

 vatus, G. gracilis, G. quadratus, G. verrucosus : but I may add, he con- 

 siders that the genus Hoplophorus of Lund should be retained, as being 

 distinct from the genus Glyptodon of Owen, being characterized by 

 its club-shaped tail; and he therefore names the G. clavicaudatus 

 H. clavicaudatus, which, however, appears objectionable, as a generic 

 peculiarity cannot be properly used as a specific designation. This 

 genus is remarkable for its great size, M. Nbdot remarking that he 

 has only observed two species, H. eupliractus, and H. Selloi, both of 

 which were of the size of an Ox ; and it may well be imderstood how 

 useful the short club-shaped tail must have been in supporting the 

 weight, probably more than 4000 lbs., of so large an animal, with its 

 covering coat of mail. It is curious that all these three genera are 

 linked together by the same dental formula, and by the same sculp- 

 tured teeth, which led to the adoption of the name Glyptodon, — the 



number and kind of teeth being the same in both jaws, viz. : |^|=32, 



whilst the formula in the Armadillo is g^=34. This group does 

 not appear to have ever migrated from the regions of South America, 

 although the Megatherium wandered more northwards ; they formed 

 therefore a local fauna of the highest interest, which is now only 

 faintly represented by the Armadillos, including the genera Dasypus, 

 Tatusia, Xenurus. M. Nodot considers, from the positions in which 

 they are found, that they inhabited the Pampas, on the banks of 

 rivers or of fresh-water lakes or pools, where they doubtless found 

 an abundance of those plants which grow in damp localities and 

 might have been easily scratched up by the slender yet rigid feet of 

 these animals. It would be unwise to accept such large additions to 

 so remarkable a group without strict scrutiny ; but it is impossible 

 to read the memoir of M. Nodot without the greatest gratification, 

 and I may add that his views on classification, and on the plans 

 of organization, are very ingenious. There appear to have been, he 

 observes, three such plans, — the first, in which the body is equi- 

 librated horizontally, the centre of gravity corresponding with the 

 centre of the axis which passes through the length of the animal ; 

 the second, where the body is equilibrated vertically, the centre of 

 gravity being behind the centre of the longitudinal axis; and the 

 third, in which the organization is sometimes conformable to the first 

 type, and at other times to the second. 



These views are illustrated in reference to the Mammalia by the 

 different modes of progression of various animals, as, for example, 



