lOf) MR. W. K. PARKER OX THE STRUCTURE AND 



Tliey are now pcrfecllij distinct from tliat floor, and a little pressure serves to sliell 

 them out under the cover-glass ; this causes no tearing of the tissue. The large 

 fenestra ovalis {f-o.) is as wide as one of the canals, and as long as the diameter of 

 an ampulla ; it lies along the middle, obliquely parallel with the horizontal canal ; 

 its antero-internal edge is double, being composed of both ^oor and capsule; the vesti- 

 bule swells out on its inner side in a crescentic manner. From the inner edffe of each 

 capsule, above (fig. 6), there is a little tract of new roof-cartilage, which will finish 

 the occipital arch. The basis cranii in the orbital region widens a little forward ; the 

 trabecules (tr.) occupy nearly a thu-d of its breadth ; the trabeculfe have met in the 

 ethmoidal region, and are becoming fused together ; tlie line of fusion is nearly equal 

 to the intertrabecular space, behind (i.tr.), which is now half filled in with new cartilage. 

 In front, the trabecules are free, diverge at more than a right angle, and curve o\it- 

 wards ; these are the horns of the trabeculae (dr.). Newer cartilage has appeared in 

 several places ; laterally, the traBeculse have grown into orbital walls, and these walls 

 are growing over the roof a little, especially in the ethmoidal region (fig. 6). Out- 

 side, in front of these rudiments of the " tegmen cranii," the " ethmoidal wings " have 

 appeared, embracing the nasal sacs (n.r.). 



Between these sacs the trabeculfe are very thick, where they are narrowest, and 

 then suddenly expand into the "cornua." These latter, or their inner edge, are 

 developing a thin, crenate expansion, ready to finish the nascd jloor. The trabeculae 

 are most compressed where they form, below, the semi-circular inner boundary of the 

 internal nostrils (^.n.). Over the sac, right and left, there is a small cartilage, like the 

 valve of a small Entomostracan, attached to the ethmoidal wing : this is the nasal roof- 

 cartilage (first " paraneural," n.r.) ; here it is more distinct than usual — more than I 

 have ever seen it in this group. 



The huge suspensorial bands reach by their distal condyles ('y.f.) in front of the 

 nasal sacs, whilst, behind, they curl themselves up against the intruded auditory 

 capsules (aw.), and bend suddenly upwards as they pass inwards, to form the narrowed 

 (but really broad) pedicle [pd.).* 



At this part the cartilage rises so high that it would seem to form the counterpart 

 of the " ascending process " of the Urodeles, but it drops again before it passes into the 

 trabecula, and although riding over the vidian nerve (VIP.) it passes under the 5th 

 (figs. 6, 7, v.). This thick high part will be further outwards, afterwards, and will 

 form the otic process {ot.p.). In front, the quadrate passes inwards as a broad lamina 

 from the saddle-shaped condyle, and grows into a hook— the pre-jialatine rudiment 

 (fig. 7) bounding the nasal passage, below, as the ethmoidal wing does, above. 



The pterygo-palatine conjugational band is short, wide, and out-turned ; on it, 

 as yet, I see no definite rudiment of the post-palatine process. Over it, from the 

 large projecting sulcate condyle for the hyoid {hy.f.), the orbitar process {or.p.) grows ; 



* The pedicle lies on a higher plane than the pterygo-palatine band ; it is, like the riljbed edge, and 

 orbitar process, a temporary tract of the suspensorium. 



