DEVELOPMENT OF THE SKULL IN THE BATRACHIA. 39 



The outworks of* this chondrocraninin are being converted into bone at various 

 points; the quadrato-jugal {(j.j.) has grafted itself on to the (juadrate (distal part of 

 suspensovinm), the long falcate palatine {jM-) is grafting itself on to the ethmo-palatine 

 bar, and the pterygoid {pg.) — a long sigmoid bone with an internal suag — is doing the 

 same to the " ^^terygo-quadrate" I'egion. 



In the Batrachia generally, the pedicle (jxl) is also more or less ossified by the 

 proper osteo-ptevijgoid; but here, as in Rana temporuria and R. p>ipi(iii'^ — that old fmh- 

 hone — the " metapterygoid " (nit.pg.) breaks out again; the possession of this centre 

 is, perhaps, the only blot in the escutcheon of our native species, — in all other things 

 the Batrachia may be said to " set their clocks " by that of Rana temporaria. 



The mandible (fig. 3) has all its pai'ts perfect or typical. 



The columella is much more developed than, but is extremely similar to, the last ; 

 it has the distinct distal segmentation (Plate 5, fig. 5), but the distal piece is now 

 contracted, like a " spatula," and has sent from its inner fece a supra-stapedial band of 

 cartilage upwards to coalesce with the under surface of the tegmen tympani {e.st., s.-st.). 



Also the large solid mass of cartilage at the stapedial end of the bony medio - 

 stapedial {m.sL) has become a separate "inter-stapedial" (i.st.), articulating with the 

 stapes (st.). 



The "annulus" (fig. 1, a.ty.) is a pei-fect ring of cartilage as in other North American 

 kinds, and as in many of those from the Oriental region. 



The "hyo- branchial" apparatus (fig. 4) is now quite normal; all the parts are fused 

 together-, are quite chondrified ; and the " thyro-hyals " are now (typically) ossified; 

 the hyoid bar {st.h.) is distinct from the ear-capsule. 



The nasals and premaxillaries, and their contiguous labials {n.,2yx., u.l^.uP.) are quite 

 normal, so also are the maxillaries {mx.); but I can find no "septo-maxillaries" — small, 

 variable, and inconstant bones ; the quadrato-jugals {q.j.), as I have just mentioned, 

 have united with the quadrate cartilage ; and the squamosals (fig. 1) are truly elegant 

 Batrachian bones, with a twisted sub-falcate upper, and a flat sigmoid lower, part. 



The "vomers" (Plate 5, fig. 2, v.) have their characteristic spikes, fore, middle, and 

 hinder ; the two latter enclosing the inner nostril {e.n., by mistake) largely ; and a 

 postero-internal, thick, dentigerous lobe. 



The parasphenoid (fig. 2, ^xt.s'., pa.s.) like that of Rana pipiens (Plates 3 and 8) 

 shows the very rare condition of a distinct bony centre for the point of this little dagger. 



These are the conditions of the growing skulls in this genus; afterwards I shall show 

 that many of the dwarfed and more or less generalised types are arrested, in some 

 things, at certain stages that correspond with growing stages of the typical kinds. 



