DEVELOPMENT OF THE SKULL IN THE BATRACHIA. 
177 
pital; the cartilage above them is ossified by the quadrato-jugal (q., q.j.). The annulus 
( a.ty.) is large, broad, and open above; the stapes (fig. 9, st.) is thick and oblique ; 
the medio-stapedial ( ru.st .) is a strong, arched rod, having a large ovoidal mass of 
cartilage on its upper fork, which, however, is not distinct as in the last kind. The 
extra-stapedial ( e.st.) is tongue-shaped ; it has a free rounded selvedge, but no 
supra-stapedial band. The stylo-hyal (fig. 7, st.h .) is confluent above ; it is very 
narrow, and widens very little in the cerato-hyal region (fig. 8, c.hy), which is a very 
narrow tape all through, with only a slight hypo-hyal lobe. The basal plate (b.li.br.) 
is largely converted into the membrane of the great front notch, which is more than 
twice the extent of the solid tract. 
The narrow ear-shaped front lobes run far along by the hypo-hyal, and the hind 
lobes are small spikes; in each of these, at their origin, there is an endosteal patch. 
The thyro-hyals (t.hy.) diverge moderately, are of the average strength, and are 
sigmoid in form; they spread well into the basal plate, proximally, and have a blunt 
unossified end. 
The mandibles (fig. 8) are extremely long and slender; the dentary (cl.) is only one- 
third as long as the ramus; the coronoid process of the articulare (ar.) is well formed, 
and the cylinclroidal condyle (ar.c.) is very large; the mento-Meckelian (m.rnk.) is 
small. 
The fronto-parietals (fig. 6, fp-) are falcate, less than a third the width of the 
narrowest part of the skull, pointed at both ends, and dilated a little behind, but far 
apart there; they just touch the ethmoidal wings in front. The nasals (n.) are long, 
narrow, angulate bones, with a small posterior and two large external emarginations. 
The marginal bones (px., mx., q.j., sq.) are all normal and well developed, but are 
thin; there is a good supratemporal plate and post-orbital spur to the squamosal; 
there is no septo-maxillary. The parasphenoid ( pa.s.) is large, long, attenuated in front, 
gnawed externally, and triangular behind. The vomers (v.) are peculiar; the front 
part is a dilated lobe, giving off a short spike in front of the inner nostril; then the 
bone runs along, flat and thin, by the inner margin of that passage up to the ethrno- 
palatine. This thin part is flanked with a thick, arcuate, dentigerous crest, and the 
right and left crests running towards each other in front, meet within a distance of 
one-third their own length. 
This large Neotropical Tree-frog has an intensely specialised skull, which, however, 
lies along a line diverging far from that of the typical skull:— 
1. The whole skull is extremely depressed. 
2. The ethmo-nasal region takes up half the length of the skull. 
3. There is only one fontanelle which is totally uncovered by the roof-bones. 
4. All but the small tracts below, and externally, and the fore end of the nasal 
region is one continuous bony box. 
5. The snout is without a rostrum (normal), but is very transverse, and the roof- 
cartilages are rather scant. 
MDCCCLXXXI. 2 A 
