DEVELOPMENT OF THE SKULL IN THE 13ATRACHIA. 243 



B. b. Toads with digital disks. 



First Family. " HYL^DACTYLiDiE." 



Ear perfect ; toes webbed ; sacral apophyses dilated ; and uo parotoids. 



Genus Callula. 

 72. Callula pidchra. — Adult female ; 2|- inches long. Pegu. 



This is one of the shortest of the Batrachian skulls ; the longest of which are short 

 compared with those of other groups. The length, including the projecting occipital 

 condyles, is scarcely more than three-fourths the breadth, but measured along the base, 

 less than three-fourths (Plate 44, figs. 8, 9). The condyles of the quadrate end a Uttle 

 behind the fore edge of the parasphenoidal wings. If the outluie of the face and 

 cheeks were produced into a whole ellipse, the short diameter of that ellipse would 

 bear, to the long, the proportion of 9 to 10. 



The retreat of the hinge of the jaw is about equal to tliat of an average skull in 

 the "Urodeles," and to what is seen in the type form at the time of transformation. 



So far as to form; as to texture and substance, this skull is like that of any ordinary 

 " Caducibranch " among the tailed Amphibia ; and quite unlike the normal Anurous 

 type of skull, for the bony tracts run past all the normal landmarks. 



As to proportion of the parts, in detail, I may instance the usually small size of 

 the " epi-hyal " element — transformed into the columella — which makes it seem, in 

 most kinds, so poor a representative of the hyomandibular of Fishes ; that is not a 

 difficulty here (Plate 44, fig. 10, m.st. e.st.), for with its iiew form and functions it 

 keeps its old size and proportions. The skull is well roofed, but much in the manner 

 of the Oriental Anura, generally ; the outer bony tracts are moderately thick, and 

 keep their sutures well. 



The occipital condyles {oc.c.) are large, bold, oval, and postero-inferior in position ; 

 they are separated by a gently emarginate tract two-thu'ds their o\\'n -o-idth. 



The foramen magnum (fig. 8) is obhque, and looks upwards ; the floor, behind, is 

 quite ossified (fig. 9, h.o.) ; the roof has an exposed pentagonal tract of cartilage 

 (fig. 8, S.O.), one side of which borders the foramen magnum ; the passage for the 9th 

 and 10th nerves is not divided. The auditory capsules show their canals strongly 

 outside (fig. 8, a.s.c, p.s.c, h.s.c), but the upper face is very much narrower than the 

 lower, so that the stapedial series is well seen from above (fig. 8, m.st.), and when these 

 are removed, the floor of the tympanum and the fenestra ovalis are seen. Beyond 

 the horizontal canal the prootic region of bone projects like a handle, and this narrow 

 prootic tract ends in a short and niu-row imosslfied tegmen tpnpani {t.t>/.), which is 

 hooked in front, and from this hook, inwards, the face of the capsule is obliquely 

 bevelled. Below (fig. 9), there is one continuous occipito-otic tract of bone from side 

 to side, cartilage only remaining {of basal oingin) to form a subconcave facet for the 

 pedicle (pcZ.), and just where, behind this part, the stylo-hyal {st.h.) is confluent. 



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