1875.] and Development of the Batrachian Skull. 139 



The labial " tape" coalesces with the trabecule, and is continued on 

 each side as a long cartilaginous string, which forms the pith of a ten- 

 tacle which reaches as far as the end of the abdomen. 



The branchial orifices are both open right and left (not the left only, 

 as in the common kinds), and the fore limbs .show their rudiments outside 

 the opercular fold. 



All the details of this, the flattest and most foliaceous of all chondro- 

 crania described, are of the utmost interest, but cannot be described 

 here. 



In this type young toads with four large legs have no trace of a 

 cartilaginous " columella ;" and yet in the adult that structure is by far 

 the largest I have yet seen, the " extrastapedial " itself being shaped 

 like a waterlily-leaf , and is relatively of the size of the whole auditory 

 ring of the bull-frog. 



This species has only one vomer and no bony palatines ; its original 

 labial band forms a pair of nasal pouches, and it acquires four more pairs 

 of these cartilages above and loses the lower pair. 



Dactylethra has the upper element of the " girdle-bone " a " super- 

 ethmoidal" plate ; but the ossification of the chondrocranium itself is not 

 in the ethmoidal but in the sphenoidal region. The huge tympano- 

 Eustachian vaults open by one orifice in the pharynx; its "interhyal" 

 is a ligament attached in the normal position ; it has two true tympanic 

 bones on each side (like those of certain birds), besides the large carti- 

 laginous annulus, and its squamosal and quadrato-jugal are more like 

 those of a tortoise than of an ordinary Batrachian. 



Its quadrate bone is ossified, as in Ganoid and Teleostean fishes and 

 tailed Amphibia. 



But the Surinam toad (Pipa monstrosa) is a rarer creature than even 

 Dactylethra, with which it agrees in being tongueless. 



The embryo is wound like a tape round the large yelk-mass ; it has a 

 gaping broad mouth, with neither labial cartilages, nor horny jaws, nor 

 " claspers." It has very small opercula, which do not cover the very 

 early formed limbs : it has gill-arches and branchial vessels ; but these 

 are not branched, for there are no gill-tufts or processes that I can 

 discover. 



The cartilaginous skull of the embryonic Pipa is a very flat leafy 

 structure, like that of the larval Dactylethra, but differing from it in 

 many respects. At this stage the fenestra ovalis is forming, but there is 

 neither stapes nor columella ; at this time there is a large " cerato-hyal " 

 in the usual place for a Batrachian larva, namely articulated to the man- 

 dibular pier not far above the condyle of the quadrate. 



In ripe young Pipos the metamorphosis is' complete, although the 

 shape of the adult skull is not attained. Ossification is already rela- 

 tively nearly perfect ; three pairs of labials now supplement the defici- 

 encies of the nasal capsule, which is but little chondrified, and in the 



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