DEVELOPMENT OF THE SKULL IN THE BATRACHIA. 223 



As In the immature skull lately described (pp. 210-212), the length and breadth 

 are equal, but the quadrate condyles (q-c) reach further back, viz.: up to the fore end 

 of the stapes (st.); a position soon attained in the young Toad. 



The occipital condyles (occ.) are large, moderately wide apart, and postero-inferior, 

 and the foramen magnum is large, as in the last (fig. 7). The auditory capsvdes are 

 also, relatively, large, and have a small, oblique tegmen {t.tij.), the whole parotic region 

 being limited to an ear-shaped process of cartilage projecting beyond the horizontal 

 canal (h.s.c), and nearly covered by the squamosal {sq.). The canals project consider- 

 ably ; in the epiotic and prootlc regions (^j.s.c, a.s.c.) equally. 



Below (fig. 2), scarcely any cartilage is left m the ear-capsules, except at the sides 

 (fig. 3); but there is a distinct tract for the facet on which the pedicle (fig. 2, j)d.) 

 ghdes. Above (fig. 1), the oblique, bevelled, outer margin is soft, and, in its defi- 

 ciency, shows the stapes {st.) and mouth of the vestibule (cm!) from that aspect. A 

 wide and rapidly widening space of cartilage remains both in the basi- and supra- 

 occipital regions (figs. 1, 2), but the bony tracts are thoroughly continuous, right and 

 left ; this is a generalised character. 



The prootic region of the bone {pr.o.) reaches half way between the 5th and optic 

 nerves (V., II.), and, above (fig. l), the bony matter only leaves a cartilaginous selvage 

 round the large, elliptical, single fontanelle {fo.), which reaches, behind, to the middle 

 of the anterior canal (a.s.c), and in front ends nearly opposite the ethmoidal wings. 



The mid skull is widish, almost oblong, widening before and behind, and slightly 

 bulging in the middle ; it is of moderate dejoth (fig. 3) and very long ; for the skull is 

 lonsf, and the bulk of the nasal regfion short. 



The girdle-bone ic'tli.) is less than the cartilaginous part behind it {o.s.), in which is 

 seen a veiy large optic fenestra (II.) ; as in many of the arrested types, the wall of the 

 mid skull opens, as it were, to the setting of the eye-balls, as the hind skuU does for 

 the ear-balls. 



The ethmoidal wings are only partly os.sified, right and left ; below (fig. 2), the 

 ethmoidal region is ossified to its end; above (fig. 1), tlie bony growth creeps along a 

 third of the true nasal region. 



The tegmen cranli is very limited before, beliind, and at the sides, so that the 

 fontanelle is very large and long. 



The na.sal roof (n.r.) is relatively very wide, as in most young Anura; the floor is 

 about three-fourths as wide (figs. 2 and 4, n.f.). The roof overhangs the fore face, as 

 in many of the edentulous types, and here there is a very generalised and very Raiine 

 prenasal rostrum [p-n.), which has, evidently, shrunk from the cavity of a {once) long 

 dermal beak, now an oval leaf of skin projecting from the nose.* 



The pro-rhinals {p.rh.) are small; the valves {u.l^.u.l-.) large; the whole region, 

 stripped of the investing bones (fig. 4), is seen to be very nnich like that of the Skate ; 



* 1 believe that thi.s type lias become dwarfed, and its rostrum shrunken as a correlatiTC of the new 

 bony tracts that liavo appeared t« mid on <he chondrocniuiuin. 



