404 ANATOMY OF VERTEBRATES. 



the skull : the pterygoids, 24, extend backward beyond them, and 

 form the sides of a deep and wide postnasal groove. The tympanic 

 bone forms the lower boundary of a hemispheric bulla, which com- 

 municates with an equal-sized cavity in the squamosal ; a narrow 

 strip of the petrosal intervenes between the tympanic and the broad 

 basioccipital. The zygomatic process of the squamosal, 27, extends 

 but little beyond the joint for the lower jaw : there is no separate 

 malar. The premaxillaries, 22, join the nasals, 15. The small 

 lacrymal, in 3Ianis longicaudata, is wedged in between the fron- 

 tal, 11, and maxillary, 21, at the anterior angle of the orbit. Two 

 tooth-like processes project from the fore-part of the alveolar 

 border of the slender under-jaw. 



In the hairy Anteater of the Cape ( Orycteropas) the petro- 

 mastoid and tympanic are distinct from each other, and retain 

 their primitive separation from the squamosals. The occipital 

 condyles are bilobed, the inferior and smaller lobe being developed 

 from the basioccipital. The zygomatic arch is slender, but entire. 

 A well-marked venous fossa depresses the inner border of the 

 foramen magnum ; the sella is large and moderately deep, with 

 anterior and posterior clinoid processes, bounded on each side by 

 the carotid channels, external to which are the deeper Gasserian 

 fosste. There are few mammalian skulls in which the cranial 

 cavity is more equally divided, than the present, into the epen- 

 cephalic, mesencephalic, prosencephalic, and rhinencephalic cham- 

 bers ; but the mesencephalic chamber contains not only the proper 

 mesencephalon, but also, as in other Mammals, part of the back- 

 Avardly developed prosencephalon, and especially those inferior 

 protuberances called *natiform.' The petrosals show very narrow 

 cerebellar fossae. The maxillary has seven alveoli, the mandibular 

 ramus has six : but the small anterior ones are obliterated with 

 the k ss of their teeth in old animals. The hyoid arch is large and 



consists of the stylohyal, cera- 

 tohyal, epihyal, and basihyal 

 ,3 \ elements, ivith the appended 

 thyrohyals, or ^ cornua majora.' 

 In the Armadillos {Dasy- 

 jms, fig. 271) the occipital plane 

 is vertical. There is no paroc- 



Skull of Basypus Peba. CLI. • • i i • • 



cipital : the superoccipital, 3, is 

 bent at a right angle to join the parietals, 7, which obliterate, as in 

 Orycteropus, the sagittal suture by their union. The mastoid is 

 perforated by a vein from the lateral sinus, and terminates below 

 in an obtuse process. The tympanic is a separate semicircular 



