DEVELOPMENT OP THE SKULL IN THE BATRACHIA. 217 



of the antorbital bar takes place. The passages for the emerging nasal nerves are 

 large, and lie on each side the square end of the far-extended ethmoid bone. They 

 lie close behind the facial edge of the snout, and on their outside the pro-rhinals 

 spring ; these ai-e hidden by the premaxillaries, and are small. 



The sinuously-transverse snout overhangs this part oBliquely ; the large external 

 nostrils (e.n.) are in its sides, and are wide apart. The roof is feebly developed, but 

 there is a well-formed pouch in the outer wall (tigs. 1, 3, al.n., n.iv.'") ; in front of the 

 nostril there is the large, oval, hollow second labial {u.l~.) ; below it, mside the vertical 

 nasal process of the premaxillary, the small, lenticular first labial (Plate .36, fig. 8, u.l^.). 

 The paIato-su.spensorial cartilage is broken up mto an adze-shaped ethmo-palatine, to 

 the under surface of which the large falcate bone (pa.) is gi-afted ; whilst the suspen- 

 sorium has a remnant of the pterygoid cartilage. 



The pedicle {pd.) is completely covered with bone, and its original apex has been lost 

 in the ossifying cartilage close to the foramen ovale (V.). The cartilage bi'eaks out from 

 lieneatli the inner foot-like ray of the pterygoid {[>g.), which has used up nearly all 

 the front process that was origmally continuous with the palatme cartilage (fig. 3, sp.). 



The suspensorium, itself, or quadrate region ((/.), is very lai-ge, and remains unossified 

 (figs. 2, 3). The condyle (f/.c.) is oblique, and reniform ; and above it a shell-hke 

 flange of cartilage grows from its outer edge, clampmg the hind margin of the long, 

 descending bar of the squamosal ; this crest of cartilage is the old " orbitar process," 

 (fig. 3, or.p) once under the antorbital, and now beneath the auditory, region. The 

 stylo-hyal (st.h.), carried back by the retreating suspensorium, but loosened from it, now 

 has grown inwards, and caught hold of the tympanic floor of the vestibule (vh.) on which 

 it is grafted. The front fork of the pterygoid bone {p<J-) is a sharp style ; the hind 

 bar is flat and vertical, buiding the inner face of the quadrate ; between it and the 

 large inner process {pd.) the Eustachian opening (eu.) is seen to be large and circular. 



The articular region of the mandible (fig. 3) is hollowed out for the reniform 

 trochlea of the quadi-ate {mk.) ; the cartilage is but httle ossified by the articulare 

 (ar.) ; the dentary (d.) is three-fifths the length of the ramus, and the mento-Meckelian 

 (in.mk.) is of the normal size. The " annulus " {a.ty.) is large and perfect. 



The stapes (Plate 36, fig. 10, ,st.) is large and sub-oval ; it has an ear-shaped boss 

 and some ossified cells ; the inter-stapedial (i.st.) is oval and semi-osseous ; it fits in 

 like a wedge between the stapes and the next segment — the medio-stapedial shaft 

 {in.st.). This part is pistol-shaped and large, it is especially thick, proximally ; joined 

 on to it is the broadly-spatulate extra-stupedial {e.st.) with its fastened, strap-like 

 process, the supra-stapedial [s.st.). 



The hyo-branchial structures (Plate 37, fig. 4) show that tliis lesser Neotropical 

 Toad is approaching its small, " glandlcss " relatives of the same region, viz. : the 

 " Phryniscidte " (Plates 40 and 41), which of all the Anura have the narrowest basal 

 plate. I shall return to this comjjarison when I come to that genus. Here the 



* The Ivwer u.l-. in fig. 2 should be n.w. 



MDCCCLXX.Xl. 2 F 



