in the Museum of Buenos Ayres. 89 



and size, forming in the beginning of the tube two circles of 

 eight small ellipses in each, and at the side three other bands of 

 other and larger ellipses ; the ellipses of the median band are 

 much larger and more extended towards the point of the tail, 

 where are to be seen two of a longitudinal diameter of 8 inches. 

 But a large part of the tail of the same species in the Museum, 

 recently discovered by roe on the banks of the river Salado, is 

 twice as long, which demonstrates that this animal was capable 

 of attaining a truly gigantic size. The distinction between the 

 three species is easy, as the foregoing description proves ; but it 

 is not easy to know whether the other species already described 

 are well founded. Mr. Owen has further accepted two species, 

 which he terms G. omatus and G. reticulatus. Of the first he 

 says that it is smaller than G. clavipes — a character which ap- 

 pears to indicate its identity with G. spinicautlus ; but, without a 

 knowledge of the shape of the tail of G. omattis, it is not possible 

 to know whether the two arc really identical or different. Of 

 G. reticulatus the author says that it is of the same size as G. 

 clavipes, but different in its structure, which is reticulate on the 

 surface of the shell-plates — a character which might apply to 

 the plates of G. tuberculatus which are situated in the centre of 

 the shell. 



The three species of Hoplophorus, founded by Dr. Lund, I 

 only know by the description of some parts which the author 

 has given in the work already cited. They show a great simi- 

 larity to the (ilyptodons of Buenos Ayres ; but, without an exact 

 comparison of tlie objects themselves, it is impossible to know 

 whether they are identical or different. 



The accounts which I have read of the work of M. Nodot state 

 that the author has established fourteen species, without specify- 

 ing their difFfrenccs ; and for this reason we cannot arrive at 

 any judgment whether thcv are well founded or not. It appears 

 that we have accepted all the species already enumerated by 

 different authors; but in this case the number of fourteen ap- 

 pears to be exaggerated, as can be proved by an examination of 

 the three different species from Buenos Ayres. 



Let us now pass to the examination of the skeleton. 



For some time the feet, the tail, and the head of Ghjptodon 

 have been incompletely known. The same statement applies to 

 the vertebral column and to the pelvis, recently described by Mr. 

 Huxley, as the skeleton which was in his hands was very defec- 

 tive, which has consequently rendered his description very in- 

 complete. 



In the Museum of Buenos Ayres there is a nearly complete 

 skeleton, known up to the present time by a photographic figure 

 made by the able artist Sefior Aldanondo (Calle Florida, 129), 



