REPORT ON THE GREEN TURTLE. 21 



Transversely Vertical Sections of the Head, from Snout to Occiput. 



First Section. — The first of these sections (PI. III. fig. 7) cuts through the horny 

 sjjike of the nose {r.sp.), and the fore part of the septum nasi {s.n.) in front of the 

 external nostrils ; it shows the thickness of the cartilage below, which afterwards foi'ms a 

 distinct descending "prenasal rostrum." 



Second Section. — The next section (PL III. fig. 8) is through the outer nostrils (e.n.), 

 and shows the same vertical cartilage a little further back ; the openings of the nose 

 are right and left of it, and these are surrounded by reniform " alinasal" cartilages 

 (cd.n.), placed back to back. 



Third Section. — This (PI. IV. fig. 8) is behind the outer opening, and brings the 

 septum nasi and aliseptal roof and waU laminae [s.n.,al.sp.) full into view. The septum 

 is thick and rounded below, narrow in the middle, then thick again where it passes into 

 the roof cartilages ; these pass down the sides into the floor, across the bottom of the 

 passage {n.p.), which is a sinuous chink, turned outwards above and below, and widest in 

 the middle 



Fourth Section. — This (PI. IV. fig. 9) is through the middle of the nose, and just 

 catches the fore part of the eyelids ; it is narrower and deeper than the last, and shows 

 the upper part of the nasal passage as a recess ; in this, as in the other sections, 

 granular tracts are seen where the investing bones will be; the osteoblasts are beginning 

 to form. 



Fifth Section. — This section (PI. IV. fig. 10) is through the back of the nose and 

 front of the eye ; the olfactory nerves (1) are seen descending through a chink which 

 corresponds to that part in the mammal which is first pectinate and then becomes 

 cribriform. This section is behind the nasal roof, and, therefore, the middle wall is the 

 perpendicular ethmoid {p.e.) ; here the nasal passages [n.p.) are deep, and theii- convex 

 face looks towards the septum ; the cartilage of each side nearly meets the septum 

 below ; the fore part of the orbito-sphenoids [o.s.) are also severed, and they are convex 

 on their inner face here. 



Sixth Section. — In this section (PL IV. fig. 11) the fore end of the hemispheres (C la), 

 and of the beginning of the olfactory tract {rhinencephalon, C 16) are seen, and the olfac- 

 tory nerves (1), still quite distinct from those vesicles, are seen running down into the 

 nasal sacs, through the right and left chinks — here non-cribriform. 



The deep nasal passage bends inwards at its lower third, and outside that bend the 

 nasal wall sends inwards a small rudiment of the " inferior turbinal " {niv.,i.th.) 



Here the perpendicular plate is very thin in the middle, for this is the part which, in 

 Lizards and Birds, becomes fenestrate. 



In this section the convexity of the orbito-sphenoids (p.s.) is outside, and not inside, . 

 as in the la.st section. 



