DEVTILOPMENT OF THE SKULL IN THE BATRACHIA. 93 



enters. The girdle-bone (eth.) is tliree-fifths the size of the orbital region and stops 

 exactly at the fore edge of the true etlnnoidal region : it does the same right and left. 



In the smaller species (Plate 16, fig. (!) a pair of secondary fontanelles exist, and 

 I have no doubt of their existence in the large kind also. The great fontanelle is not 

 very large and. is covered in well by the roof-bones [f.p-)- 



That which strikes the eye at once in this skull is the tumid shape of the whole nasal 

 region, wliich is large in eveiy direction, along, across, and from top to bottom. It is 

 well roofed by cartilage (al.n.), but the floor (fig. 2) is still more extensive; in front, 

 the snout is broad and gently convex, not produced, but rounded in the middle and 

 rising well over the openings (e.?(.). Below (fig. 2), the growth of cartilage is 

 unusually extensive, the angles of the subnasal laminae (on each side of s.n.) are large 

 and falcate ; the pro-rhinals (jxrh.) are long, wide, and somewhat decurved bands ; 

 the wall of the nasal capsule (fig. 3, n.iv.) is well developed. But the greatest modi- 

 fication is seen in the large size of the ethmo-palatine arms (e.pa.), which however 

 have no definite pre-palatine spike (pr.jjct.). The bony bars correlated with these 

 ai-ms are also very large ; they are falcate, with the point growing back under the 

 post-palatine cartilage (fig. 2, pa.). 



Here we have also what is seen in several Toads, viz. : an additional semi-distinct bony 

 bar, sharp and denticulated, stuck to the lower surface of the main bone at its middle. 



The pterygoids {2^9-) are slenderer than the palatines ; they have used up the feeble 

 cartilaginous tract to which they were applied ; they fork in fi-ont of the Eustachian 

 opening (fig. 2, cv.) at a right angle, and thus that large space is itself triangulai'. 

 The part covering the pedicle ( pd.), and faced with unaltered cartilage, is very long and 

 pedate, for this point is not far outside the foramen ovale (V.). The hind part of the 

 pterygoid faces the inside of the strong suspensorium, whose condyle (q.c.) is a large 

 and well made trochlea. There is some deposit of bone in the quadrate region from 

 the quadrato-jugal {q., q-j). 



The annulus (figs. 1 and 3, a.ty.) is large and perfect; the stapes (figs. 1, 2, 5, si.) is 

 oval, umbonate, and cut away in front ; the columella has a condyloid cartilaginous 

 proximal end without a segment ; and the strong bony bar (in.st.) has two projecting 

 "trochanters." The extra-stapedial (f..sf.) is tongue-shaped, and its ascending process 

 [s.st.) is confluent above. 



The mandible (fig. 3) is strong ; the condyle {ar.c.) is large and reniform ; the coro- 

 noid crest {ar.) is not high ; the dentary {d.) is only half as long as the ramus ; the 

 mento-Meckelian {in.itih.) is well developed. 



The stylo-hyal {st.h.) is confluent above, the rest of the band (fig. 4, c.hy.) is narrow 

 up to the hypo-hyal lobe iji.hy.) ; the notch is very lai-ge, leaving a basal plate {b.h.br.) 

 of small extent at the middle ; the fore side lobes are very large, elegant, and reni- 

 form ; the hind lobes are narrow arcuate bauds ; the thyro-hyals {t.hij) ave rather 

 straight and of moderate size ; between them there is a lozenge-shaped ossification 

 of the basal plate (h.hr.). 



