68 ZOOLOGY OF THE VOYAGE OF THE BEAGLE. 



tenths. The crown of the tooth presents no protuberances, but resembles that of 



the Sloth ; the roots are hollow."* 



Meg 



the absence of other proof of the identity of species, in which, as may be seen by 

 comparing fig. 2, with fig. 4, in PL XVII., the teeth differ widely in form, it 

 would be obviously hazardous to adopt such an approximation on hypothetical 

 grounds.f In order, however, to obtain more satisfactory evidence of the nature 

 and amount of the difference between the Megalonyx laqueatus, and the allied 

 animal represented by the above-described fragment of lower jaw, I wrote to my 

 much respected friend M. Laurillard, requesting him to send me a sketch of 

 the teeth in the cast of that lower jaw, which had been transmitted from New 

 York to the Garden of Plants. With full confidence in the characteristic precision 

 and accuracy of the drawing with which I have been obligingly favoured by M. 

 Laurillard, I am disposed to regard the amount of difference recognizable in every 

 tooth in the lower jaw in question (fig, 3 and 4,) as compared with the molar tooth 

 either of Megalonyx Jeffersonii (fig. 1,) or Meg*, laqueatus (fig. 2) to be such as 

 to justify its generic separation from Megalonyx on the same grounds as Mega- 

 lonyx is distinguished from Megatherium, and for the subgenus of Megatherioid 

 Edentata, thus indicated, I would propose the name of Mylodon. % The species of 

 which the fossil remains are described by Dr. Harlan may be dedicated to that 

 indefatigable Naturalist who has contributed to natural science so much valuable 

 information respecting the Zoology, both recent and fossil, of the North American 

 continent. The fossil about to be described represents a second and smaller 

 species of the same genus, and I propose to call it Mylodon Danvinii, in honour 

 of its discoverer, of whose researches in the Southern division of the New World 

 it forms one of many new and interesting fruits. 



* Harlan's Medical and Physical Researches, 1835, p. 334. M. de Blainville speaks of a cast of a fragment 

 of a lower jaw " portant encore cinq dents en serie ;" as having been transmitted to the Museum of the Garden 

 of Plants from North America, together with other bones, all of which he refers to the genus Megalonyx ; M. 

 de Blainville does not describe these teeth, which is to be regretted, inasmuch as, if he be correct in regard to 

 their number, which can hardly be doubted, and if he wrote with any clear and definite ideas of the generic 

 characters of Megalonyx, this would indicate that Megalonyx differed generically both from Megatherium and 

 Mylodon in a more important dental character than has hitherto been suspected (See " Comptes Rendus, &c." 



1839, No. V. p. 142.) 



t Dr. Harlan also indicates differences in certain parts of the skeleton of the New York fossils as compared 

 with his Megx. laqueatus ; but thinks them probably due to a difference in the age of the individuals : he says 

 " There is also in Mr. Graves' collection, in New York, a tibia, nearly perfect from the right leg ; the segment 

 of a flattened sphere, on which the external condyle of the femur moves, is rather more depressed, than in the 

 specimen from Big-bone-cave. Other marks and peculiarities are observable on this bont), not found on that of 

 the Megalonyx laqueatus of Big-bone-cave, but they are probably due to a difference in the age of the 

 individuals ." Loc. cit. p. 335. 



% Mv\rj, mola ; odovg, dens. 



