314 



^IR. W. K. PAEKEE OX THE STEUCTUEE 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 base 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 vii. 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, ^.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 [al.e.) in front, and overlap 

 the auditory capsule {au.) behind, exactly as in Eschricht's figure of the embryo of 

 Balcena japonica {op. cit. plate ii. figs. 1 & 2, Jc,^mG). ■ 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 orbitd-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 fossae, but, as in the embryo of the Ostrich and 

 Fowl (" Fowl's Skull," Plate Lxxxr. fig. 4, etit.), 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 olffictory 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 «& G, o.s.) the alisphenoids arc 

 obscurely seen {al.s.), overshadowed and obscured by the so-called "alee minores." 

 Tlicy have no foramina in their substance, but the cranial nerves root down in front of 

 ■and behind them ; on the upper view tlic whole of the alse and the floor of the " sella 

 turcica " arc far from the eye, the posterior clinoid wall {p.cl.),th.e end of the investing 

 mass, cropping up high into the cranial cavity. The car-sacs are seen from without, 



