Description of the Bones of a new Fossil Animal. 73 



in the lower jaw, like the same in the Megalonyx laqueatus, is 

 about double the width of the others, and resembles somewhat 

 two molars, united in the middle by a compressed bony ridge ; 

 PI. I, fig. 1. It is about equal in length to the others, (the 

 lower extremity is fractured in the present specimen,) and two 

 inches in its long diameter, the crown varying from four to eight 

 tenths in lateral diameter. The anterior or tusk-like molar is 

 more than four inches in length, (vid. PI. I, fig. 5.) There are 

 two other specimens of tusks, belonging to a younger individual, 

 rather shorter, more slender, and almost cylindrical in form. 



Maxillce. — We have observed in this collection only the four 

 fragments above noticed. A portion of inferior jaw is three inches 

 deep, and two inches thick ; Plate III, figs. 1 and 4 — a section of 

 the anterior end. A fragment of upper jaw is much thinner; the. 

 crowns of the molars here scarcely project above the rim of the 

 sockets. The alveoles are distinct, and the teeth are separated 

 from each other from one and a half tenths to four tenths : Plate 

 III, fig. 3. Plate III, fig. 2, a portion of lower jaw, and figs. 5 

 and 6, sections of anterior ends of figs. 2 and 3. 



Os humeri. — There are two humeral bones in the collection, 

 that now described being a portion of the skeleton of much 

 greater dimensions than the individuals from which the other 

 bones were obtained ; in fact, the animal of which this humerus 

 formed a part, must have approached in size the megatherium, 

 judging from the massive structure of the bone, and from its 

 length, being little more than six inches shorter than that of the 

 megatherium. 



This humerus belonged to the right side ; its general form is that 

 of the megatherium, and is yet more massive, presenting stronger 

 marks for the attachment of its powerful muscles ; it is destitute 

 of the large foramen near the internal condyle, which distin- 

 guishes this bone in the megalonyx, orycteropus, and most other 

 genera of this order. In the proportional width or transverse di- 

 ameter of the condyloid crests, it resembles the same bone in 

 the megatherium, which is likewise destitute of the foramen 

 above noticed ; in the last mentioned animal, this transverse di- 

 ameter is one half the length of the humerus, this part being 

 always greatly developed in such animals as possess great mus- 

 cular power in their fore-arms and hands. Thus, in the orycte- 

 ropus this diameter is three fifths of the length of the humerus; 



Vol. xliv, No. 1.— Oct.-Dec. 1842. 10 



