DEVELOPMENT OF THE SKULL IN THE BATRAC1IIA. 
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17 (continued).—(E) Skull of adult Pseudis paradoxa. —Old male; 2d indies long. 
Surinam. (Hyrtl’s prepn. in Mus. Coll. Surg., Eng.) 
The specimen whose skull is here figured was evidently a very old individual; it is 
therefore of great value in this series.* 
It is at once seen to be a very generalised type (Plate 10, figs. 1-4), sharply 
separated from a normal Frog, such as Rana temper aria. 
The skull is one-half the length and a little more than half the breadth of that of 
the perfect larva. 
The skull of the nearly metamorphosed larva (D) is five-sixths the length of that of 
the adult: so that after lessening much, it enlarges again, a little. 
About the size of the skull of a large Common Frog, it is more elegant in shape, 
being a very perfect semi-ellipse in outline. 
The well-bent bow formed by the two series of cheek bones has its “horns” meeting 
at a sharpish angle, for the parts in front are modelled on three trabecular outgrowths, 
the “pro-rhinals” and a small “prenasal.” 
The complex structures that run across, behind, from one cheek to the other, are 
also very beautiful in their construction (Plate 10, figs. 1-3). 
The hind part of the skull is densely ossified from the occipital condyles to the optic 
foramen (oc.c., II.), and in front the ethmoidal girdle-bone (eth.) occupies the hind half 
of the nasal capsule below, and all but the edge in front; the parts in front of that, 
and the anterior sphenoid ( o.s .), are unossified. 
The occipital condyles are rather wide apart, being separated by a large semicircular 
emargination; they are hemispherical and subpedunculate, as in those Urodeles that 
have an intercalary “ odontoid ” vertebra. 
Below (fig. 2), the auditory masses seem to stand out in a directly transverse line; 
but above (fig. 1), they are seen to turn forwards as well as outwards, and the well- 
marked semicircular canals (between pr.o. and e.o.) are some distance from the edge, 
which is flanked by the squamosal (sq.) : the intervening part is the ossified “ tegrnen 
tympani.” 
The gently rounded floor of the vestibule (fig. 2) shows no trace now of that 
Selachian development of the basal plate, outside the capsules, which formed the 
tympanic floor. 
The main nerve-passages (fig. 2 ; II., V., IX., X.) are well seen from below ; the two 
hinder passages are separated by a bony bar ; the “foramen ovale ” is enclosed in bone, 
and the optic fenestra is partly margined, also, by the extended alisphenoidal wing of 
the prootic (pr.o.). 
The foramen magnum has less roof than floor ; neither of these plates has any 
divisional line as in a normal Batrachian. 
* It is a most fortunate thing for me that our College has possessed itself of this invaluable specimen; 
it is not an easy thing to get an adult. 
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