1 62 



PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. 



ing the Santa Cruz Gravigrada, as a group, can be made only with 

 reservations, since full information is available with reference to but one 

 of the three families. 



Ameghino has already given a summary of the more important structural 

 features of the Santa Cruz Gravigrada ('94^, 141), but much additional 

 material has been gathered since that account was written and this mate- 

 rial permits a somewhat more extended description. In what follows, 

 however, there is necessarily much repetition of Ameghino's generaliza- 

 tions. 



( i ) Like the other Santa Cruz edentates, the Gravigrada are far smaller 

 in stature than their Pleistocene successors ; many of them are exceed- 

 ingly small and only one or two are large enough to rival the lesser 

 Pleistocene genera, such as Nothrotheriwn (Ccelodon] and Scelidotherium. 



FIG. 14. 



Upper teeth of Santa Cruz Gravigrada, x \. a, Hapalops indiffcrtns ; b, H. eloitgatus ; 

 c, Mcgalonychothenum atavus ; d, Analcimorphus giganteus ; e, Schismothcrium splcndens ; 

 f, Pelecyodon cristatus ; g, Hyperleptus garzonianus ; h, Planops magnus. 



(2) No trace of dermal ossifications has been found in connection with 

 any of the skeletons. At first sight, this may seem surprising, but it 

 should be remembered that an exoskeleton could be expected to occur 

 only in the MylodontidcE and that the material representing this family in 

 the Santa Cruz beds is so rare and so imperfect that the negative evidence 

 is without weight. 



(3) With the possible exception of TfetnatJieriinii and certain very 

 doubtful forms, the dental formula is invariably f; the teeth may be in 



