DEVELOPMENT OF THE SKULL TX THE BATRACHIA. 77 



indeed now, it will soon become less than one-fourth its present size. Even now it 

 is less than a fourth tiie size of tliat of the young Tadpole (A, Plate 2). 



Relatively to the cranium, it is immense, yet, and retains all the larval characters, 

 being still confluent with the chondrocranium at three places. 



The pedicle {pd.) is now a very narrow baud, and like the pterygo-palatine, is at 

 I'ight angles witli the main bar. 



The "elbow" of the suspensorium has developed a new "otic process" (ot.p.), and 

 the spiracular band has become a mere thread (Plate 11, figs. 6, 7, sp.c). 



As in the " Urodeles," the permanent "otic process" (ot.p.) mounts up against the 

 fore edge of the tegraen tympani and the swellings caused by the ampullar : it reaches 

 inwards, as in them, to the anterior ampulla, and even a little further. 



Above (fig. 6), it is a thick, rounded mass, but below (fig. 7), it is flat ; it lias, as it 

 were, been thrust back against the auditory mass, and cleaves to, and lies outside, 

 as well as in front of it. 



The greatly developed ridge on the edge of the suspensorium, instead of passing in 

 a gentle arc forwards to become the thickened edge of the orbitar process, turns 

 suddenly as a round loop, and then, at an acute angle, bends back ao-ain round the 

 front margin of the orbitar process, scarcely dying out as it approaches the condyle of 

 the quadrate, in the front of the face ; all this growth is ready to vanish away. 



This swollen upper selvedge is thickest behind, then narrows up to the apex of the 

 orbitar process, and keeps its breadth until it dies out in front. 



The quadrate region and condyle (Plate 11, figs. G, 7; and Plate 12 fig. 1, q.) is 

 very broad and also thick, especially at its outer edge. 



In conformity with the divergence of the quadrate bars the mandibles (Plate 12, 

 fig. 1, mk) are considerably longer ; but the lower labials (U.) are full sized, as yet, 

 and the condyle f )r the hyoid {hy.f.) is perfect. 



So also is the bar itself {c.hi/.), but one can see that the styloid region {st.h.) is 

 elongating. 



In the Common Frog and Toad there is no upper hyoid element until about three 

 months after the loss of the tail ; in P.seudis the tail has lost onlv two-sevenths in 

 length, although nmch narrower, when that element (the epi-hyal or " columella ") 

 appears. Here, at any rate, this rod appears much earlier, relatively, than in the 

 common kinds ; it is possible, however, that tlie Tadpole, at this stage, may be several 

 years old. 



In these large Tadpoles it is as easy to show tliat the early " stapes " belongs to the 

 periotic capsule as that this late segment does not. There are two cartilages, besides 

 the stapes, in certain "Proteidea" {e.g., in the Menopome), both inside the facial nerve. 

 The upper piece sends its narrow proximal part to the stapes; the lower cartilage, 

 manifestly part of the epi-hyal, becomes partly confluent v/ith the hind margin of the 

 suspensoriiun. 



Here things take a veiy diiferent course, for the cartilage (Plate 11, figs. 8, 9) is 

 undivided, and forms a rudimentary epi-hval. 



