166 
MR. W. K. PARKER ON THE STRUCTURE AND 
columella is large and bilobate behind, but the unossifiecl part is not distinct from the 
medio-stapedial ( m.st .). The decurvecl extra-stapedial (e.st.) is spatulate, and it gives 
off a narrow supra-stapedial (s.st.), which degenerates into a ligament, above. 
The stylo-hyal ( st.k .), 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.br .) is 
wide ; the plate is short and wide, and the fore lobes are uncinate and but little wider 
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-brancliial bone. The mandible 
(fig. 3) is long and slender, with a pyriform condyle ( ar.c .), a long dentary and mento- 
Meckelian (d., on.ml:.), and a low coronoid ridge to the articulare (ar.). 
The investing bones are 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 (fp-), which are delicate styles over¬ 
lapping the girdle-bone in front, and only forming a wall-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 “ tegmen ” 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 (mx.) is of great length, 
almost reaching to the hinge (//.c.), but it is thin and not high ; the small t-ootli-like 
quadrato-jugal (q.j.) is partly joined to the quadrate (q.). 
The squamosal (sq. ) runs one-third 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. 
The vomers (v.) are like bony spiculse ; there is a po.sUnarial, but not a pre- narial 
hooked spike; the £! body ” is in two arcs, the hinder ends in a thick lobe covered with 
teeth, and the front lobe is pointed and underlies the angle of the floor-cartilage ( s.n .). 
The main points to notice in this skull, as compared with the ££ norma,” are its 
general arrest at a condition of growth equal to that of a young Common Frog of the 
first summer. The particular points are :■— 
1. Rudiments of a basi- and supra-occipital. 
2. Its one large fontanelle. 
3. The long orbital fontanelles. 
