XIIL] EDENTATA. 231 



cavity, and freely communicating with it, is a considerable 

 air sinus, formed between the pterygoid (Pt) and the ali- 

 sphenoid (AS), and causing an oval prominence in the side 

 of the palate. 



In another species of the same family, Tamandua tetra- 

 dactyla, there is a second similar but smaller sinus anterior 

 to this, in the side of the palatine bone. 



The mandible is very long and slender, with an exceed- 

 ingly short symphysis, no distinct coronoid process, and 

 a slightly elevated, elongated, flattened, condylar articular 

 surface. 



The anterior cornu of the hyoid is very long and slender. 

 Its proximal end is ligamentous, and its distal portion con- 

 tains three distinct ossifications. The thyrohyals become 

 united by bone to the very narrow basihyal. 



The skull of the little Tree Anteater (Cydoturus didac- 

 tylns) besides being shorter, and much arched in the longi- 

 tudinal direction, differs mainly from that of Myrmecophaga 

 in not having the long canal of the posterior nares closed 

 by bone below, as neither the pterygoids nor the greater 

 part of the palatines meet in the middle line. The 

 tympanic is more bullate. The mandible has a pro- 

 minent, narrow, recurved coronoid, and a well-developed 

 angular process ; it is strongly curved downwards in front. 



In the Armadillos of the restricted genus Dasypus, in- 

 cluding D, sexcinctus, villosus, and mimtttts, the cranial 

 portion of the skull is broad and depressed ; the facial 

 portion triangular, pointed in front, and much depressed. 

 The anterior narial orifice is small, terminal, and directed 

 forwards and downwards. There is a completely ossified 

 tympanic bulla, ankylosed with the rest of the skull, per- 

 forated on the inner side by the carotid canal, and con- 

 tinued externally into an elongated bony meatus auditorius, 



