280 PALEONTOLOGY. 



have been between nine and ten inches. All the ridges were covered with a layer of cement, 

 (Figs. 1 and 2, a a,) but in many places it had become accidentally detached. Near the 

 base of the tooth it had the thickncs.s of one fourth of an inch. The enamel which invests the 

 base of the crown is tuberculated throughout; and between the bases of the transverse ridges 

 are to be seen at the outer border longitudinal ones, the upper edges of which are more or less 

 multifid. Each transverse ridge is composed of two very unequal portions separated by a deep 

 cleft : one portion consisting of a very large conical tubercle, with a smaller one attached to, 

 and as it were impressed into, the side towards the axis of the tooth ; the other portion is com- 

 posed of three tubercles of more nearly equal size, of which the outer one is the longest, all 

 closely jjacked together ; the cleft between these two portions, as seen on the broken anterior 

 end, is one inch and a quarter in depth. A large tubercle is found in the middle of the 

 space between the anterior and second ridges ; also two smaller ones between the second and 

 third ; in both cases connecting two adjoining ridges with each other. 



The unequal division of the transverse ridges, and the strongly tuberculated enamel on the base 

 of the crown, do not appear to be represented in any of the different figures of the teeth of Mas- 

 todons, except, perhaps, in one instance, the molars fi-om the Camp de Geans, figured by Cuvier, 

 where there is an indication of a longitudinal tuberculated ridge ; but the other peculiarities 

 indicated above are not apparent. Were it allowable to establish a species on the authority of 

 a single tooth, it might be done in the i3resent instance; but, before such a step is taken, other 

 specimens should be examined, in order to ascertain how far these individual peculiarities are 

 constant. 



If it be referable to either of the species referred to above as coming from South America, 

 it would be to the larger species, where the molars are from nine to ten or more inches in 

 length, viz: M. Humholdtii — M. Andium being applied to designate the smaller species. 



III. Fragment of a femur. — This is the lower portion of the thigh-bone of the right leg. It 

 does not appear to be wholly mature, as the line of separation between the epiphysis and the 

 shaft of the bone is still distinct, though the co-ossification of the two has taken place. The 

 following measurements give the dimensions and proportions : 



Inches. 

 Breadth through tuberosities -------8 



Breadth across condyles ........ *i 



Breadth of inner condyle -------- 3| 



Breadth of outer condyle - - - - - - - -3| 



Length of inner condyle --------5 



Length of outer condyle --------4 



Breadth of groove for patella - - - - - - -3| 



Length of groove for patella -.-----4| 



Breadth of interval between condyles ------ 0| 



Dearth of interval between condyles ------ 1^ 



The inner condyle is the longest and most prominent, but the difference in length is less than 

 in 31. cjiganteus. The interval between the condyles dilates anteriorly into a pyriform space, of 

 aboixt one inch in its transverse diameter, for the attachment of the crucial ligament. The 

 whole fragment is nine inches in length ; and on the fractured end, which is triangular with a 

 flattened apex, it measures seven inches in its transverse and four in its anterior-posterior 

 diameters. 



Note. — Since the preceding descriptions were written, Lieut. Gilliss has forwarded to me 

 another molar of a 3Iastodon Andium, more recently received by him from Prof. Domeyko, 

 of Chile. It was taken from Lake Tagua-Tagua, and belongs to the same species as the lower 

 jaw already noticed. Its dimensions are as follows : 



