DEVELOPMENT OP THE SKULL IN THE BATRACHIA. 211 



to project from an arc of a large circle ; thus the outline of the whole is like that of a 

 short egg. 



The pattern of a Batrachian chondrocranium is here perfect ; and this has, already, 

 been modified by two pairs of bony centres that are enclosing the 9th and lOtli nerves, 

 behind (IX., X.), and the 5th and 7th (V.) in front of the ear-sacs (an.). The occipital 

 condyles (occ.) are large, sub-reniform, near together, and postero-inferior. 



The foramen magnum {f-m.) is very large; each ear-sac projects far outwards as a 

 parotic process, whose outer edge is the tegmen tympani (t.ti/.). The floor is perfect 

 (fig. 8), the roof as complete as in the " norma," there being one large, and two small, 

 oval fontanelles {fo., Jo'.). Infero-laterally, there are the nerve passages, and that 

 for the optic nerve (II.) is a large fenestra — not a mere foramen. 



The ethmoidal -wangs pass as yet right into the antorbital bars [e.pa.), and then, 

 again, into the pterygoid fore-growths of the quadrate cartilage. 



The roof of the nose (fig. 7) is not clearly divided off from the septum {s.n.), and the 

 floor (fig. 8) is about equal to it. 



The jDrenasal end of the septum is a small bud, and the pro-rhinals {p.rh.) are veiy 

 small points of cartilage that look inwards ; the angles of the floor are sub-falcate. 



The labials {u.l^.n.l'-^.) have their permanent form and relations. The /"-shaped pala- 

 tine is applied to the ethmo-palatine bar, which is dilated in front, externally, as the 

 adze-shaped pre-palatine. The post-palatine cartilage is dilated to a less degree and 

 ends, regionally, but not by division yet, in front of the great opening for the temporal 

 muscle. There the pterygoid region begins, which narrows, somewhat, and then 

 dilates to make its forks ; its bony plate (jtg.) is already broad and Bufonine. Under 

 the main foot of this bone the cartilaginous pedicle (jjc/.) is dilated, but does not lose 

 its continuity (as far as I can find, here, certainly not in B. vulgaris) with the basis 

 cranii. 



The quadrate condyle (q.c.) is large and rcniform ; the Eustachian passages (eu.) 

 are small ; the stylo-hyal {st.Ji.) is imiting with the skull, and passes outwards under 

 the projecting, car-shaped, tegmen tympani. The stapes was not chondrified in the 

 larva just described, but that process took place very soon afterwards ; now, there is a 

 columella (fig. 9, co.). 



Tins new cartilage, which appears in the beginning of summer, is a thick oblique 

 wedge, helping the solid stapes (st.) to iill the fenestra ovalis; it is arched above and 

 concave below, and ends in front as a fine thread of long cells. '•■ 



The small " spiracular cartilage," which had undergone various fortunes in the larval 

 state — sometimes fixed at one end and sometimes at the other, and then free — is now 



* This is the state in which this organ was shown to be in young specimens of B. vulgaris by Professor 

 Huxley in the early summer of 187-1. My own dissection of this stage is shown in my second paper on 

 the " Batrachian Skull " (Phil. Trans., 187(5, Plate 55, fig. 8, co.) ; it is somewhat more advanced than this 

 ■whioh I am now describing in another species. 



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