A Remarkable Ground Sloth 9 



Malleus. — The left malleus has fallen out of the ear opening. It is probable that 

 all of the ossicles of the right side are in situ, but the soft parts prevent their study. 

 The malleus is typical, with a rounded head bearing two faces and a slender manu- 

 brium. It measures 12 mm. There are no other processes such as one sees in man. 



Dentition (Plate III). — Comparing our skull with Stock's Figure 13, the 

 main distinctions are: In the former the teeth are closer together, the second upper 

 molar has a much deeper notch on the occlusal surface, and the anterior crest is much 

 higher than the posterior one. M 5 seems to be of less fore and aft diameter as com- 

 pared with the others and has a slight vertical groove on its anterior face. In Stock's 

 figure this face is convex. The fore and aft diameters of all the other teeth correspond 

 with the figure, but the transverse diameters are somewhat less. In our specimen the 

 transverse notches are wider toward the outer side; in No. 1 800-11 Stock's series the 

 reverse is true; while in 1800-4 the transverse crests are parallel. These distinctions, 

 however, are merely those of wear and are not diagnostic. 



SKULL AND JAW MEASUREMENTS 



Skull 



Length, maxillae to occipital 

 Width of cranium behind orbits 

 Ratio of length to width 

 Length of palate 

 Width of palate 

 Height of occiput 

 Length of nasals 

 Width of muzzle 



Mandible 

 Length, symphysis to condyle 

 Length of symphysis 

 Depth between 2d and 3d molars 

 Height, angle to coronoid 

 Thickness of horizontal ramus at m a 

 Ratio of length to height 



VERTEBRAL COLUMN 



Vertebral Formula.— No complete series of thoracic vertebrae was obtained 

 from the Rancho la Brea. Mr. Stock's estimate of seventeen, however, agrees with the 

 Yale specimen and is therefore correct. The number of caudals cannot be verified from 

 our individual, as the distal ones have not been recovered as yet. 



