270 PEOF. W. K. PAEKEE ON THE STETJCTUEE AND 



the same plane as the investing mass from which they arise ; but below (figs. 4 & 5) 

 they project, being thick, oval in section, or compressed. 



Behind and below they would seem to be articulated to the moieties of the 

 " investing mass ;" but they are really continuous, and do not form so distinct a joint 

 as in Chelone ("Turtle's Skull," op. cit. pi. 2. figs. 6, 7), This apparent distinctness of 

 the trabeculse as seen from above and below is partly due to the fact that the internal 

 carotid artery {i.c) is entering the skull at that part. 



Yet these inferior projections may be taken as the apices of the trabeculee, and these 

 projections backwards into a cartilaginous " lingula " (see " Fowl's Skull," Phil. Trans. 

 1869, pis. 81, 82, Ig) is for the purpose of forming a root, from which may grow the 

 copious periosteal laminse that form each " anterior tympanic recess." 



The fore half of the chondrocranium is not finished by the trabeculee. I have just 

 spoken of an intertrabecular bar {i.tr) ; this large and important element is nearly as 

 distinct in the Crocodile as in the Green Turtle {op. cit. pi. 2. figs. 6, 7, i. tr, pn). This 

 agyzous prepituitary element helps the winged trabeculse to finish the foundations of 

 the skull in front ; it is a solid subfalcate plate or bar, with its convex margin above, and 

 its concave outline below. The lower edge is thick, but subcultrate behind, where it is 

 jammed in between the trabecule ; it projects a little into the pituitary space {py). In 

 front (figs. 4 & 5, i.tr) this bar has become lessened, and it curves downwards behind the 

 frontal wall of the head, as the prenasal rostrum {pn ; see also " Fowl's Skull," pi. 81). 

 The trabeculse do not end at the part where they embrace the intertrabecula, but run 

 along its upper part as thin laminae, and then break out, right and left, as the large 

 adze-shaped orbito-sphenoids (Fl. LXIII. figs. 5, 6, and PL I^XIV. figs. 1, 2, tr, i.tr, o.s). 



These " anterior sphenoidal wings " form nearly half of the lateral part of the skull ; 

 they touch the small " posterior wings " {al.s) by their more extended hinder wing-tip, 

 and by the lesser front tips they grow up to the nasal sacs {ol), walling in the 

 " rhinencephalon " (fig. G, C") on the outside. These elegant wings are convex above, 

 near the middle, but become sinuous externally, their margin is convex above, before 

 and behind it forms a concave line. 



The large optic nerves (ii) escape behind the orbito-sphenoids, close to the part where 

 the trabeculae flatten themselves against the intertrabecular wall. 



The pituitary body {py) is still a racemose mass, behind which we see the hooked 

 notochord {nc), the emarginate ascending wall of the investing mass {p.cl), and behind 

 this the basilar artery {b. a). 



The nasal capsules (PI. LXIII. figs. 3, 4, and PI. LXIV. fig. 1, ol) are scarcely carti- 

 laginous as yet ; but the auditory sacs have a more solid wall (PI. LXIII. figs. 4, 6, 8, 

 PI. LXIV. fig. 4, and PI. LXVIII. fig. 3, au) ; this is still distinct from the investing 

 mass {iv). Each capsule is now of a pyriform shape, broad in front, narrower behind, 

 and lobate on the inner face, whence the membranous labyrinth is giving off the rudimen- 

 tary cochlea {chl). The horizontal and posterior canals can be seen from below, shining 



