with its aperture directed upwards and backwards. The zygoma is complete. The pterygoids are small, and send no horizontal plates inwards to complete the bony palate, as in the Anteater. The mandible has a well-marked ascending posterior portion, supporting a transversely extended condyle, and a high, slender coronoid process.

In all the other genera of Armadillos, Chlamydophorus excepted, the tympanic is a mere half-ring, loosely connected with the surrounding bones.

The hyoid arch is strongly ossified. The anterior cornu consists of three bones. The thyrohyals ankylose with the basihyal.

In the Scaly Anteaters or Pangolins (genus Manis), the skull is somewhat in the form of an elongated cone, with the small end turned forwards, and very smooth and free from crests and ridges. The occipital plane slopes upwards and forwards. There is no distinction between the orbit and the temporal fossa, which together form a small oval depression near the middle of the side of the skull. There are short zygomatic processes on the maxilla and the squamosal, but the arch is incomplete in most species, owing to the absence of the malar. There is likewise no distinct lacrymal bone. The plane of the anterior narial aperture looks forwards and upwards. The premaxilla is produced along the side of the nasals towards, but not reaching, the frontals. The palate is long and narrow. The pterygoids extend backwards as far as the tympanics, but do not meet in the middle line below. The tympanic is ankylosed to the surrounding bones, and more or less bullate, but not produced into a tubular auditory meatus. The hinder part of the squamosal is often dilated with air-cells, forming a rounded prominence at the outer posterior angle of the skull.

The rami of the mandible are edentulous, very slender and straight, without any angle or coronoid process. From near the anterior extremity of the upper edge a sharp conical tooth-like process projects upwards and outwards. The condyle is a slightly expanded flattened surface, not raised above the level of the rest of the ramus.

In the Cape Anteater (Orycteropus) the skull is moderately elongated and dilated in front of the orbits. The facial portion is subcylindrical and slightly tapering. The lacrymal forms a considerable part of the side of the face. The zygoma is complete and slender. There is a small postorbital process. The premaxillæ are short and widely separated from the frontals. The palate ends posteriorly in the thickened transverse border of the palatines, and is not continued back by the pterygoids. The tympanic is annular and not ankylosed to the surrounding bones.

The mandible is slender anteriorly, but rises high posteriorly, with a slender recurved coronoid, and an ascending pointed process on the hinder edge below the condyle, which is small, oval, and looks forwards as much as upwards.

The hyoid arch is completely ossified. The basihyal is a thin bar, narrow in the middle. The thyrohyals are not ankylosed to it. The ceratohyals are thick. There is a small (apparently epiphysial) ossification between the epihyal and the stylohyal.

The Three-toed Sloths (genus Bradypus) have a high compressed skull, and an extremely short face. The cranial cavity is oblong, and rather high and compressed. There is no fossa on the periotic for the flocculus. The olfactory fossæ are large. The plane of the occiput is vertical, or sloping slightly forwards and upwards. The frontal region

is dilated with air sinuses. There is a smali postorbital process. The lacrymal is very small, and the canal is external to the margin of the orbit. The malar is attached to the frontal, lacrymal and maxilla in front, curves downwards and outwards, and then divides into a descending and a high ascending branch; but neither of them join the straight zygomatic process of the squamosal. The nasals are short and wide. The anterior nares are nearly vertical, or rather inclining downwards. The premaxillæ are exceedingly rudimentary, only the palatal portion being present, without any ascending process; they unite with each other across the middle line, but not with the maxillæ, hence they are generally lost in macerated skulls. The palate is narrow, especially posteriorly, and not produced behind the molar teeth. The pterygoids form large plates with prominent rounded borders, compressed in some, and inflated in other species. The glenoid fossa is narrow from side to side. The tympanic, squamosal, and periotic are ankylosed together. The former forms a considerable bulla, but no tubular meatus. There are large supratympanic air sinuses, and a well-marked ossified tympanohyal.

The mandible has a comparatively high horizontal portion, rounded in front with a very small median triangular process at the upper border. The coronoid process is high and slender. The condyle is small; its articular surface is convex from side to side, short and nearly straight from before backwards. The angle forms a broad compressed posterior projection, with a slightly incurved lower border.

The stylohyals are large, compressed, and curved, with a prominent posterior process near their upper end. The basihyal is small, and ankylosed with the thyrohyals, so that they form together a V-shaped bone.

The skull of the Two-toed Sloth (Cholapus didactylus), though generally similar to the last, presents in some points marked deviations from it. Even in aged specimens, in which almost all the sutures are obliterated, the tympanic is a mere ring, incomplete at the upper margin, and but slightly connected with the other bones around. The premaxillæ are more developed, and become ultimately ankylosed with the maxillæ. The pterygoids are much smaller, but sometimes are bullate.

The upper margin of the mandible is produced anteriorly into a spout-like process. The condyle is scarcely above the level of the molar teeth, and is wide from side to side. The angular projection is smaller and thicker.

The hyoid (in an old specimen) has a strongly ossified anterior arch, consisting of two bones of nearly equal length, the proximal one with a stout-rounded process projecting backwards and outwards from near its upper end. The second is bent at a right angle near its lower end, and may result from the ossification of two elements. The basi- and thyro-hyals are ankylosed to form a wide U-shaped bone.

Order MARSUPIALIA.—The skull of the large carnivorous Marsupial, the Thylacine (Thylacinus cynocephalus), resembles so closely that of a Dog in its general aspect, that it will be well to commence an account of the peculiarities of the crania of Marsupials generally by comparing these two skulls.

It will be seen by the section (Fig. 70) that the brain cavity of the Thylacine is very much smaller than that of the Dog (Fig. 46, p. 117) in relation to the size of the rest of the cranium, or to that of the whole animal, a sign of great inferiority of organisation. This diminution affects chiefly the cerebral fossa; the cerebellar fossa is nearly equal in size, but it is placed more directly behind the cerebral, and is

not in the least overlapped by it, as in the Dog. The occipital plane is vertical, or even inclining forwards above. The tentorial plane is nearly horizontal. The olfactory fossa, though smaller in vertical extent than that of the Dog, is more produced anteriorly. Thus in form, as well as in relative size, the cerebral cavity is far more reptilian than that of the Dog. The basicranial axis is very straight, and

FIG. 70,-Section of the skull of the Thylacine (Thylacinus cynocephalus), MT maxilloturbinal; ET ethmoturbinal; ME ossified portion of mesethmoid; Fr frontal; Pa parietal; SO supraoccipital; ExO exoccipital; Per periotic : BO basioccipital; Sq squamosal; AS alisphenoid; BS basisphenoid; OS orbitosphenoid; PS presphenoid; Pt pterygoid; Pl palatine; Vo vomer; Mx maxilla; PMx premaxilla; cd condyle of mandible; a angular process.

is continued forwards in the same line by the basifacial axis. The pituitary fossa forms no distinct impression, and there are no posterior clinoid processes. The ossified portion of the mesethmoid (ME) is extensive, and terminates anteriorly in a nearly vertical line. The vomer (Vo) very shallow from above downwards. The turbinal

is