16G MR. W. K. PARKER ON THE STRUCTURE AND 



columella is large and bilobate behind, but the nnossified part is not distinct from the 

 medio-stapedial [m.st.). The decurved extra-stapedial (e.st.) Ls spatulate, and it gives 

 off a narrow supra-stapedial (s.st.), which degenei'ates into a ligament, above. 



The stylo-hyal (st.h.), from its junction with the pedicle, runs into the cerato-hyal 

 (fig. 4, c.hy.), without change of breadth ; the hypo-hyal region {h.hy.) is narrower, and 

 there is no projecting lobe. The great notch in front of the basal plate (b.h.bi-.) is 

 wide ; the plate is short and wide, and the fore lobes are uncinate and but little wnder 

 than the hind lobes. The thyro-hyals are long, a little more than half bony, and 

 hooked inwards behind. There is an irregular patch of "endostosis;" between these 

 bars, in front, as the sign of a tendency to form a basi-branchial bone. Tlie mandible 

 (fig. 3) is long and slender, with a pyriform condyle (to-.c), a long dentary and mento- 

 Meckelian (cL, m.mh.), and a low coronoid ridge to the articulare («'•.). 



The investing bones ai'e extremely delicate, some of them being less than may be 

 seen in the Tadpoles of other kinds, before the fore legs are free. 



This is true, especially of the fronto-parietals {f-P-), which are delicate styles over- 

 lapping the girdle-bone in front, and only forming a xvaU-plate to two-thirds of the 

 narrow marginal band of roof-cartilage. In the temples each bone projects, and binds 

 upon the anterior canal ; behind, it becomes pedate, not reaching, however, to the 

 small ex-occipital ; thus the hinder, complete " tegraen " is nearly all naked. 



The nasals {n.) have a fuller development, but they are more than their own width 

 apart, and are thin lunate shells. The premaxillaries {px.) are extended in front of the 

 wide snout, and the main bar of each is long ; their nasal and palatine processes are 

 moderately developed. Over the junction of these bones with the maxillaries there is a 

 small irregularly radiate septo-maxillary {s.mx.) ; the maxillary {inx.) is of great length, 

 almost reaching to the hinge ('/.c), but it is thm and not high ; the small tooth-Uke 

 quadrato-jugal {q.j.) is partly joined to the quadrate (7.). 



The squamosal (.s-^'.) runs one-tlurd further forward than the tegmen (fig. 1, left of 

 au.); it overlaps that eave a little, and is .split at its free postorbital end ; the descend- 

 ing part is normal. The parasphenoid is thin and like that of a Tadpole, but it reaches 

 from the front of the " cephalostyle " (b.o.) nearly up to the notch in the margin of the 

 narrow girdle-bone [eth.) ; its processes are all normal, but the lateral wings are rather 

 limited, and the hind lobe is irregular. 



Tlie vomers (i'.) are Uke bony spiculse ; there is a posi-narial, but not a ^re-narial 

 hooked spike ; the " body " is in two arcs, the hinder ends in a thick lobe covered with 

 teeth, and the front lobe is ])ointed and underhes the angle of the floor-cartilage {s.n.). 



The main points to notice in this skull, as compared with the " norma," are its 

 general ari'est at a condition of growth equal to that of a young Common Frog of the 

 first summei". The particular points are : — 



1. Rudiments of a basi- and supra-occipital. 



2. Its one large fontanelle. 



3. The long orbital fontaneUes, 



