NATURAL HISTORY MISCELLANY. 165 
this difference, however, may be the result simply of the displacement 
forwards of the first molar, as appears to be the case with some varieties 
muscle arises. The bone in Megathere at this point, viz., on ei 
of the insertion of the deltoid, being broad and flat, while, in Megalonyx 
and Mylodon especially it forms, with a marked prominence on the out- 
side of the bone, a large hollow surface looking outward and backward, 
for the origin of the external part of the muscle, and which large and 
deep groove seems to have been filled up by it. The distal extremity of 
is int 
all probability the nerve and artery passed in their course to the forearm. 
Fourth.— The astragalus of the Megalonyx, Dr. Leidy says ** bears much 
whole weight of the leg upon the inner side of the foot." 
Fifth.— The cubitus of Mylodon, as figured by Dr. Harlan, very 
slightly resembles either that of Megathere or Megalonyx. 
From the few facts above stated, it would be unwise to draw hasty con- 
clusions, and if the three genera have a common parentage it would be 
difficult to say to which genus the first pair belonged. Are there not, 
Hipparion, Anchitherium and Equus, which have been brought forward 
by Professor Huxley in confirmation of Mr. Darwin's hypothesis ? 
marked 
Boston. 
No less marked will appear the mechanism of the elbow joint in all 
the genera of these digging animals, and the upper or mashing surface 
of their teeth, so characteristic of all the Megatheroid tribe — the sur- 
face presenting at one time ‘‘a transverse sulcate plane, at another, ex- 
cavated in the midst, with prominent margins." — H. €. PrRkINS, M.D. 
THE TERTIARY BEDS OF THE AMAZON. — Up to December, 1867, no fos- 
sils had been observed in the peculiar variegated clay formation which 
overspreads the great valley of the Amazon. At that time I was sojourn- 
ing with my friend Hauxwell at Pebas, where I discovered a multitude of 
