324 University of California Publications in Geology [Vol. 8 



from the skull, being firmly attached in but a single specimen. The 

 upper and middle forks of the malar are usually of unequal length 

 and have generally the proportions noted in M. robustus. Several 

 malars in the collection have their upper and middle forks subequal. 

 The lower and middle forks are separated by a wide notch as in M. 

 garmani. The lower folk is narrower than in the South American 

 species. 



The premaxillary of M . harlani resembles in general structure that 

 of Mylodon garmani. It differs from M. robustus in the more acute 

 angle formed by the median and lateral wings, the narrower anterior 

 end, and the much greater length of the median wing. It differs also 

 from M. garmani in having the tip slightly more rounded. In the 

 two specimens examined the median length greatly exceeds the cor- 

 responding length in M. garmani, but judging from the depth of the 

 median anterior notch of the maxillary this length must vary. 



The median wing of each premaxillary is greatly widened dorso- 

 ventrally along the sutural union with the opposite element, while the 

 lateral wing is compressed dorso-ventrally with the outer margin 

 somewhat thickened. At the inner angle formed by the two wings, a 

 canal opens anteriorly upon the ventral surface and represents prob- 

 ably a portion of the anterior palatine foramen. The premaxillary 

 is pitted to a greater or less degree. 



The palate is noticeably convex antero-posteriorly between the third 

 and fourth superior teeth. Transversely it may be slightly convex, 

 flat, or even concave. Just anterior to the second teeth or between 

 these teeth the palate may be either slightly or deeply concave in the 

 median line. Between the last teeth and posterior to them the palatine 

 surface is concave, but may show various degrees of elevation along 

 its median line. The postpalatine notch may either be acutely or 

 broadly rounded. 



The pterygoids flare outward and diverge more or less posteriorly. 

 They resemble Brown's specimen in size, differing in this regard from 

 the Colorado skull described by Cockerell. Their surface form in 

 general is similar to that in M. garmani. Between the pterygoids the 

 basi-cranial region may vary in width as in Mylodon robustus. The 

 small bone described by Allen as the tympanic is present in a single 

 skull, being broken away in most of the specimens. It resembles that 

 in M. garmani and M. robustus in general structure. The foramina 



