DEVELOPMENT OF THE SKULL LN" THE BATRACHIA. 165 



ovalia (V.) on theii" upper edge, reaching from thence to the pedicles {pd.). Beyond 

 the horizontal canal the capsule lessens to one-tliird its breadth, to form the "tegmen" 

 (fig. 1). The fore and hind skulls are equal in length ; the mid skull is one-half longer, 

 and relatively broad ; its sides are sinuous, for it dilates a little both in the temporal 

 and ethmoidal regions. The actual floor of the chondrocranium is only half the width 

 of the roof, and the optic nerves (II.) pass out of the end of a long, oval fenestra, which 

 reaches to witliin a short distance of the ethmoidal wings. Measured from the hinder 

 margin of the actual optic foramen to its fore end, tliis fenestra takes up four- fifths of 

 the orbital wall, and the girdle-bone (eth.) does not even reach to the fore edge of the 

 fenestra. A narrow band of cartilage bounds the single, great fontanelle (fo.), and as 

 this widens in front it becomes bony ; the fore margin of tlie fontanelle is bony, but the 

 tegmen cranii thus ossified is a veiy narrow selvedge, and this band only reaches to 

 the very definitely marked nasal roofs, whUst the bone runs very slightly into the 

 septum (s.n.). Laterally, there projects a narrow superorbital eave beyond the bone, 

 and the ossification projects shghtly into the wings. 



The nasal septum [s.n.) is thick behind and bulbous in front ; its junction with the 

 roof-cartilages is shown in front, where the short decurved " rostrum" (p.n.) has a small 

 projection on each side of it, the 7'ight being the largest ; these are the ends of the 

 crescentic roof-tracts, wliich are large and wide. 



Below (fig. 2) the floor is very wide, and ends in front in the primary angles of the 

 cornua trabeculte, and in the smaller, secondary, decurved pro-rhinals {s.n., 2)-rh.). 



The narial openings are wide apart, the external nostrils (e.n.) being three-fourths 

 the distance from each other of the inner holes [i.n.) ; the outer openings are protected 

 by the normal valves {u.l^.u.P.). The palato-suspensorials are slender, but quite 

 normal ; from the ethmoidal wing, which thickens round the hinder margin of the 

 inner nostril, the ethmo-palatine becomes a moderate tape of cartilage, expanding 

 into the spiked pre-palatine band, which runs backwai'ds as a post-palatine, with a 

 rounded hinder lobe projecting into the maxillary, and then becoming pterygoid 

 [pr.pa., pcj.). The forks of the suspensorium are apparently nearly equal, as seen 

 from above and below, but the quadrate i-egion and its condyle {q.,q.c.) pass further 

 backwards, reachmg as well some distance downwards and outwards. The palatine 

 bone {pa.) is the normal falcate thin piece, and the pterygoid {p(J-) has the usual 

 shape, but, contrary to rule, it covers the cartilage most above and least below. 

 The bulbous pedicle is most seen above ; below, it is confluent with the stylo-hyal {pd., 

 st.h.) — a rare modrfication, and seen again in Phyllomedusa bicolor (Plate 34, fig. 8). 

 Above, in front of the fork, the pterygoid-bone is rough and hollowed out ; it is thin and 

 lathy where it binds on the inner face of the quadrate. That region is only slightly 

 ossified by the quadrato-jugal {q.j.) ; its condyle (7.0.) is large, elegantly bilobate, with 

 the inner or hinder lobe much the larger of the two. 



The annulus {a.ty.) is rather small and open above ; the stapes (fig. 5, st.) is oval, 

 with an emargination antero-superiorly, and an external boss. The pistol-shaped 



