314 
MR. ~W. K. PARKER OK THE STRUCTURE AND 
sphenoid. The real harmony between the outstanding bars on each side this bone and 
the basipterygoid spurs of the Lizard and Ostrich is here clearly shown; whilst the 
“ external pterygoid plate ” was only studied in Man (where it is said to be merely a 
periosteal outgrowth of the “ ala major ”), its homology with the “ Sauropsidan ” bar 
could not be determined ; here it is a direct cartilaginous outgrowth of both lase and 
wing , and its basal origin is from the side of the trabecular apex. Here it articulates 
with both palatine and pterygoid, being so huge and developed to so great an extent 
laterally ; there (see “ Ostrich’s Skull,” Plate yii. fig. 4, pg., a.p.) the pterygoid is 
wedged in bodily between the basipterygoid spur and the palatine; it is in that memoir 
called the “ anterior pterygoid process” (a.p.), and by Professor Huxley “ basipterygoid” 
(“ On the Classification of Birds,” Proc. Zool. Soc. April 11th, 1867, p. 418). There is 
no special ossification in the confluent trabecular base beneath the orbito-sphenoids 
(figs. 2 & 5, p.s.), and these large wings have no centre over and behind the optic fora- 
men, as in Man (figs. 1, 5, 6, o.s., 2); from these only the whole mass will be leavened. 
These wings have now coalesced with the lateral ethmoid ( ol.e .) in front, and overlap 
the auditory capsule ( au .) behind, exactly as in Eschricht’s figure of the embryo of 
Balcenci japonica (op. cit. plate ii. figs. 1 & 2, JcfmG). The orbito-sphenoids are now at 
their highest degree of development (see in third stage, Plate XXXIII. fig. 3, o.s., and 
in the sixth, Plate XXXV. figs. 1, 3, 4, o.s.). In front of these orbito-sphenoidal 
nuclei there is no endosteal deposit, nor is there any for some time to come in the ear- 
sacs (au.). The bird’s-eye view (fig. 6) shows how far, as in the Bird, the great septum 
of the nasal sacs (“ mesoethmoid,” continuous perpendicular plate, and septum nasi) 
continues backward beyond the primary roof (here compare fig. 6 with primordial stru- 
thious skull, op. cit. Plate vii. fig. 1, al.e., cr.g., o.s.). The cribriform plate is now suffi- 
ciently advanced on each side of the retral septum of the sacs to be fairly understood ; it 
is a delicate comb-shaped lamina of secondary cartilage, with four long “ teeth ” growing 
inwards and forwards from its margin or “ back ;” the long interspaces admit the olfac- 
tory filaments. The common outer band does not fill in all the space which forms the 
floor to these huge rhinencephalic fossge, but, as in the embryo of the Ostrich and 
Fowl (“ Fowl’s Skull,” Plate lxxxi. fig. 4, eih.), the septum is continued backwards to 
the verge of the anterior sphenoid, and here, in the Pig, ends in a club-shaped manner. 
Between the anterior edge of the orbito-sphenoid (o.s.) and the back of the comb-like 
lamina (figs. 5 & 6, cr.l.) there is a considerable membranous space. The bulgings in 
the olfactory roof (al.e., al.s.) are caused, behind, by the upper and middle turbinals, 
now increasing in complexity, and further forwards by the inferior turbinals. Behind 
the postneural commissure of the orbito-sphenoid (figs. 5 & 6, o.s.) the alisphenoids are 
obscurely seen (al.s.), overshadowed and obscured by the so-called “ alee minores.” 
They have no foramina in their substance, but the cranial nerves root down in front of 
and behind them ; on the upper view the whole of the alee and the floor of the “ sella 
turcica ” are far from the eye, the posterior clinoid wall ( p.cl .), the end of the investing 
mass, cropping up high into the cranial cavity. The ear-sacs are seen from without, 
