220 
ME. W. K. PARKER ON THE STRUCTURE AND 
Between the sides of the palatine plates of the palatine hones and those of the 
maxillaries there is an oblique, fusiform fenestra. The former bones {pci.) are like two 
blades, they are closed, at their suture, which is nearly half as long as the maxillary 
suture, and have their handles behind the hard palate. On each side, at their broadest 
part, they nearly touch the alveolar plate of the last tooth ; they then bend inwards and 
become a mere oblique short tract of the wall of the nasopalatine passage. This 
wall is finished by the pterygoids (pg.), which are bent inwards and downwards also, 
behind, where they are capped with a nucleus of cartilage ( pg.c .); their basicranial 
llange is moderate and continuous. There is no mesopterygoid centre. The tympanic 
( a.ty .) is a narrow U-shaped bony staple, with its fore limb sinuous, and lobate at its 
end. 
The vomer (figs. 4 and 6, v.) is an extraordinary structure; the main median bone 
is relatively smallest in the Marsupials, and largest in the Tenrec, if we except the 
abnormally long-faced Cetacea.* 
The low septum (fig. 6, s.n .) and the large thick vomer (v.) at once suggest the com¬ 
parison with those of the Cetacea. This bone overlaps two-thirds of the recurrent 
cartilages (rc.c.), becomes roughly carinate, pinches in a little, and then gives off an ala, 
right and left of the sharp split in its hinder end. The whole bone is rough and 
cellular, and in the hind part is undergoing absorption along certain lines, the meaning 
of which we shall see in the next stage. 
O 
Second Stage q/’Centetes ecaudatus (continued).— Endocranium and visceral arches. 
The exposed part of the nasal labyrinth—the snout ( cd.n .)—is barrel-shaped ; the 
nostrils are latero-terminal; the rest of the large labyrinth is not figured, but I have 
shown the septum (fig. 6, s.n., p.e.) and the recurrent cartilages (figs. 4—6, rc.c.); these 
are tongue-shaped, scooped tracts, and are quite normal. The highest part of the 
perpendicular ethmoid (fig. 6, p.e.), between the large oblique olfactory fossae is in 
reality low, but the septum nasi, proper (s.n.), is a crest to the huge, thick intertra¬ 
becula, scarcely higher than that bar. Where the septum divides the snout, there it 
becomes deficient, and, indeed, the partition in front of that oval fenestra is mainly 
formed by the fusion, back to back, of the alae nasi (cd.n.) ; the snout is bent 
downwards considerably. 
The basis cranii behind the perpendicular ethmoid (figs. 4, 5,t p.e.) is beginning to 
ossify as the presphenoid, but the independence of this centre is doubtful in this case, 
as the orbitosphenoids (o.s.) have met over the middle bar (fig. 5) and are closely 
embracing it. These wings are about two-thirds the size of the alisphenoids (cd.s.), 
already they are quite ossified and have lost the large superlateral tract of cartilage, 
* Tli is species —Centetes ecaudatus —is the one land Mammal that rivals the Whale in the relative 
length of the head—it is one-third of that of the body. 
f Eigs. 4 and 5 are from the dissected endocranium after it had been pressed out so as to display the 
parts. 
