no 



PATAGONIAN EXPEDITIONS: PAL/EONTOLOGY. 



plates with the central groove, also at the angles of the peripheral figures, 

 and much the same- is true of the head-shield and tail-sheath. In Eucine- 

 Peltus the ridges marking the lines of suture between the coalesced plates 

 have quite large and conspicuous pits, and they are also unusually well 

 marked in Metopotoxus. In the posterior portion of the tail-sheath, where 

 the plates have no ornamental pattern, the pits are situated somewhat ir- 

 regularly around the borders of the plates, except in Asterostemma, which 

 seems to lack them entirely. 



6. The teeth of the Santa Cruz glyptodonts differ from those of the suc- 

 ceeding genera in their less extreme hypsodontism, in their less symmetrical 



c 



FIG. 10. 



Skulls of glyptodonts, left side, x \ ; a. Glyptodon asper (after Burmeister) ; b. Propalceohop _ 

 lophorus australis ; c. Eucinepeltus complicatus (mandible from E. petestatus). 



form and in the greater simplicity of the anterior ones, although in the 

 Pampean Sclerocalyptus - and - are still very simple. Almost every well 

 preserved specimen of Propalaohoplophorus shows one or two minute 

 alveoli in each premaxillary, which apparently served for the insertion of 

 vestigial incisors, but the teeth themselves have not been observed and 

 were probably shed or resorbed at an early period. The functional teeth, 

 always f in number, differ relatively little in the various genera, but each 

 genus may usually be identified from the teeth alone. Thus, in Astero- 

 stemma the posterior upper teeth (^-^-) show no sign of a division of the 



