'6 :\rR. W. K. PARKKE OX THE STRUCTURE AND 



The ethmoidal wall behind the nasal sac was articulated to the " tegmen cranil " 

 (Plate 2, fig. 1); that joint was lost in the last (Plate 11, fig. 1); now a new 

 articulation has appeared, namely, of the post-palatine crest with the ethmoidal wall 

 (Plate 11, fig. G, pi. pa..); this, however, is merely at its upper part; the bar is 

 continuous with the skull below (Plate 1 1, fig. 7, J^pg.)- 



The direction of the endoskeletal palatine (" post-palatine ") was directly forwards 

 (A) ; tlie pre-palatine point being slightly turned inwards to join tlie trabecula by a 

 ligament (Plate 2, fig. 1, pt.p)a., pr.p)ci-)- 



Afterwards (B, Plate 11, figs. 1-3), the pre-palatine point was well developed, and 

 tin-ned directly inwards to join the trabecula, but the main piece was parallel with the 

 skull ; the sharp crest had become an even thick ridge. 



Now (C, Plate 11, fig. G ; and Plate 12, fig. 1, pt.pa.), this part has behaved like a 

 railway signal : it has turned outwards, almost directly, but is bent a little forwards ; 

 the pre-palatine has again become reduced to a mere point carrying the ligament that 

 i-uns to the cornu trabeculfe. 



The flat, but crested, bar (A, Plate 2, fig. \, pt.pa.) has become a massive, rounded 

 rib of cartilage, standing high above the thin pterygoid pltite that unites it with the 

 suspensorium (Plate 11, fig. 6, p.pg) ; thus that outer bar now stands off a good 

 distance from the skull. 



The tegmen cranii has grown well over the perpendicular ethmoid, and the septum 

 nasi has become surmounted by a pair of thick crescentic folds, lying back to back 

 (Plate 11, fig. 6 ; and Plate 12, fig. 1, al.-tp.) ; from these the cartilage grows to some 

 little distance over the nasal sacs, but I cannot find, either now or afterwards, any 

 such clearly distinct nasal roof as is seen in the species of Rana. 



The anterior part of the skull has become reduced in size and modified to a much 

 greater extent that the outer bars; thus the quadrate hinges (</.) are now a sensible 

 distance in front of the cornua trabeculoe. 



These latter parts are now very small and bifurcated ; the Inner lobe is a short hook, 

 {c.t7'.) pointed inwards ; this will be the pro-rhinal, it lies in front of the nasal sac ; the 

 outer lobe is a long "ear" of cartilage (s.n.I.) directed outwards and little forwards, 

 and attached by ligament to the prae-palatine spur [pr.pa.]. 



The position of the pre-palatine ligament shows the amount of lessening the 

 trabecular cornua have undergone, for the ligament and this outer cornu, together, 

 form the fore boundary of the internal nostril (i.n.). The last stage (Plate 11, 

 figs. 1, 2, c.tr.) shows how much of the cornu there was then in front of that passage. 



The etlimo-palatines meet below (fig. 11, p-pg.); there was no such appearance in 

 the last stage, before these bars had turned round (fig. 2) ; here, if the segmental nick 

 (fig. 6), which is seen above, had extended between the post-palatine and the trabecula, 

 it woidd have severed it from the skull, beneath which the right and left bai's are 

 confluent. The sub-cranial confluence is peculiarly Petrorayzine. 



The huge suspensorium (sp., q.) is being folded up that it may be changed ; huge 



