98 MR. "\V. K. PARKER ON THE STRUCTURE AND 



The interorbital regioa is rather pinched than swollen in the midcUe, and gently 

 narrows, forwards ; from the hind margin of the optic fenestra (II.) to the front of the 

 true ethmoidal region, half beliind, is cartilage, and half, in front, is bony; the latter 

 tract is the " girdle-bone " {eth.). This bone has a convex fore, and a concave hind, 

 margin ; it nearly reaches the fontaneUe above and spreads a little into the ethmoidal 

 wings, right and left. There is no trace of a superorbital "eave." 



The nasal region is normal as to its wide floor (s.n.l.), gradually lessening, backwards; 

 it has large pro-rhinals {p.rh.); and it wants a pre-nasal rostrum ; but the roof (fig. 1) 

 is very narrow, and the thick wedge-shaped end of the septum nasi {x.n.) is ossified 

 separately: this bone {p.n.) is a low triangle, with its apex backwards. 



The large sub-oval orbital spaces, and the strongly bent bow of the palato-suspen- 

 sorial are normal, but wider than usual; the pterygoid bone (pg.), with the pedicle 

 (pd.), are also normal; but the palatine bone (p«.) is composed of two sub-equal 

 pieces. These are large in proportion to their cartilaginous model, and the outer 

 piece is large and falcate. The quadrate hinge (q.c.) is normal ; above it the quadrato- 

 jugal (q.j.) has ossified a good tract of the cartilage. In the rounded angle formed by 

 the foi'ks of the pterygoid the Eustachian passage (eu.) is of medium size, is oblique, 

 turning outwards and forwards. 



The "annulus" {a.ti/,) is broad, rather small, and imperfect above; the stapes 

 (fig. 4, St.) is large, oval, sub-pedunculate, and obliquely emarginate on its antero- 

 superior edge. 



The columella (fig. 4) is pistol-shaped, there is no interstapedial cartilage separate 

 from the medio-stapedial; this bar is gently arcuate {m.st.), and ends in a broadly 

 spatulate extra-stapedial (e.st.) with a strong supra-stapedial (s.st.) confluent above. 



The mandible (fig. 3, d., ar., m.mk.) is perfectly normal, and so is the hyo-branchial 

 apparatus; the stylo-hyal (fig. 2, st.h.) is articulated, above. 



The investing bones (figs. 1, 2) are on the whole similar to those of a Common Frog 

 of the same size, but they are less solid. The parasphenoid (jJa.s.) has a similar form, 

 and so have the vomers (?;.) ; these, however, are turned outwards nuich more. The 

 pre-maxillaries, septo-maxillaries, maxiUaries, quadrato-jugals, and squamosals have 

 the typical form, but are all rather feeble. 



But the fronto-parietals (/p.) are very arrested ; and although they reach from the 

 ethmoidal wings to the junction of the anterior and posterior canals {a.s.c, p.s.c.) they 

 are each only two-thirds the width of the naked space between them. 



The contrasts between tliis and the typical skull arise mainly from the following 

 characters : — 



1. There are no secondary fontanelles. 



2. The fronto-parietals are abortively developed, leaving the fontanelle largely open. 



3. The occipito-auditory ossifications, right and left, are generalised, and not properly 

 divided into prootics and ex-occipitals. 



4. There is an " anterior septal bone " in the nasal region. 



