21 G MR. W. K. PARKER OX TJIH STRUCTrHK AXU 



G2. Bufo ?•?(«< MS. —Adult female ; 2^- inches long. South America. 



This species should be put into the next genus, viz.: Otilophus; the difference 

 between the skull of this and of a young 0. margaritifer is very much less than what 

 may be seen between several kinds of Bufo. 



The general form of the skull is that of a triangle with the apex off ; the length is 

 nine- tenths as great as the breadth. 



Some of the characters of B. agiia are exaggerated in this ; although its size is only 

 a third of that large species. 



That which especially strikes the eye in this skull, and in the exaggerated form seen 

 in the next genus, is the pi'ojection of the square snout forwards over the marginal 

 bones of the face. 



This form of the nasal region occurs amongst the Ganoids in the " Palseoniscidae " 

 (Teaquaie, Trans. Palaeont. Soc, 1877, plate 1, figs. 1, 2, 11), and is exactly repeated 

 in the half-ripe embryo of the Pig (Phil. Trans. 1874, Plate 34, figs. 1, 2, 6). In this, 

 as in many other things, the Anura prefigure the Mammalia. 



The occipital condyles (Plate 37, figs. 1-3) are large postero -inferior, and reniform ; 

 they are sepai-ated by a shallow notch less than their own width. The epiotic eminences 

 (fig. 1, e.o.; fig. 3, ej).) are almost flush with the occipital condyles; the quadi-ate 

 condyles {q.c.) only reach back to the inter-stapedial, the supra-temporal plate (sq.) 

 as far as to the middle of the stapes (st.). This top of the squamosal, growing so far 

 backwards, gives the squareness and breadth to the outline of the skull, beliind. 

 Like that of many of the Caducibranchiate Urodeles, the endocranium is almost 

 entirely ossified into one continuous bony box : there may be a little cartilage at 

 the tegmen tympani ; there is a tract in front, for the fore half of the nasal region 

 is soft. The parotic parts are large but do not reach out beyond the middle of their 

 squamosal roof. The rim of the occipital arch, the superoccipital region, and three- 

 fourths of the ear-capsules are naked above. Also a small lozenge of the ethmoid 

 (fig. 1, etli.) is seen in front of the frontals, and the cartilaginous snout is bare at its 

 fore margin. Through the broad roof (fig. 1, f.ji-) the three fontanelles shine : the 

 first is large and heart-shaped, the two small spaces are sub-oval, and lie at a moderate 

 distance behind the emargination of the main space. 



Below, as in B. agua, the outline of the endocranium is very irregularly sinuous ; 

 it is very broad behind, then lessens up to the axillae and ala3 of the ethmoid (eth.), where 

 it expands suddenly ; in front, the hone inms up to the j)oints of the palatine processes 

 of the premaxillaries (fig. 2, px.). 



The outline of the far overhanging roof is sub-pai"allel with the edge of the endo- 

 cranium, being dominated by it. Each '"'eave'' is more than half the width of the 

 cranial chamber. Seen from the side (fig. 3), this chamber is extremely shallow — as in 

 other Neotropical Anura — much more so, relatively, than in B. agua. The ethmoidal 

 wmgs are ossified to their proper end, where, in the genus Bufo, the segmentation 



