T)KVKLOPMENT OF THE SKULL IN THE BATRACHIA. 251 



near the remarkable modifications seen in Pii^a (ibid., Plate 62, figs. 2 and 9, sq.) ; in 

 that strange type the outer and middle ear meet in, and cover, a curious spoon-shaped 

 j)rocess of the squamosal. 



The parasphenoid (fig. 2, pa.s.) is evidently large, but its boundaries are very indis- 

 tinct through anchylosis; it has between its three main rays a rather rare " apophysis;" 

 this is a transverse, rounded projection, looking forwards, and downwards ; it has a 

 hollow in front of it, and a mammillate elevation behind. 



There is not a trace of the i-ight and left vomer ; in this, agam, we see a character 

 in which this type agrees with Pipa. 



But Ilt/lajAetiia agrees in some important characters with the other Aglossal type, 

 viz. : Daetyletlira (Phil. Trans., 1876, Plate 59). Tliis similarity is to be seen in the 

 Salamcmdrian extension of bone in the endocranium ; in tlie superior aspect of the 

 occipital condyles — not to the same extent, but as much seen above as below ; in the 

 huge size of the " middle ear," and especially its inter- and extra-stapedial elements. 

 [ look upon these similarities rather as an expression of the generahsed nature of both 

 kinds than as suggesting genetic relationships. 



With the adopted and natural " norma" the skull of Ilylaplesia presents remarkable 

 contrasts ; they may be summed up as follows : — 



1. The general form of the skull is as much longer than what is typical, as that 

 of Callula is shorter. 



2. The great breadth and strength of the cranium as compared with the feebleness 

 of the face. 



3. The arrested retreat of the quadrates and their condyles. 



4. The extreme breadth of the muzzle. 



5. The intense ossification of the endocranium, and the anchylosis with it of the 

 investing bones. 



6. The absence of vomers. 



7. The apophysis on the parasphenoid. 



8. The sviperior as well as inferior aspect of the occipital condyles. 



9. The small size of the tympano-Eustachian cavity, and the increase of room in 

 that " cleft" by the hollowing out of the squamosal, above. 



10. The very open annulus and large stapes. 



11. The huge size, relatively, of the columella, and especially of its proximal and 

 distal elements. 



12. The large size of tlie three pairs of labials — the lower as mento-Meckehans. 



13. Tlie presence of a considerable pre-orbital besides the septo-ma.xillary. 



14. The reversed position of the hypo-hyal lobe, the smaUness of the basal plate, 

 and large size of the thyro-hyals. 



These are some of the more outstanding peculiarities of this strong little skull, whose 

 generalised nature is shown, also, hi its unlooked-for agreement with the archaic and 

 non-typical skulls of the " Aglossa." 



2 K 2 



