DEVELOPMENT OF THE SKULL IN THE BATRACHIA. G9 



1. The septo-maxillaries are suppressed (?). 



2. The fronto-parietals confluent behind. 



3. The pro-rhinals doubled over as hooks. 



4. A distinct sharp prenasal. 



5. Very narrow nasal roofs. 



6. No inter-stapedial segment. 



7. No supra-stapedial band. 



8. A large long luicinate " extra-hyal." 



The folding over of the pro-rhinals, the length of the prenasal, the generalised state 

 of the columella, and the additional hyoidean element, indicate a very marginal posi- 

 tion for this type in the Family "RanidfB." 



Second Family. " Cystignathid^." 



First genus. Pseudis. 



17. (A) Skull of Psevdis jxtradoxa. — First larva ; total length, 10^ inches; head and 

 body, 3^ inches ; tail, 7 inches ; greatest width of tail, 4 inches ; depth of body, 

 zj inches ; hind legs, ^ inch. S. America. 



A side view of this, the youngest and largest Tadpole of Pseudis (natural size) (Plate 1, 

 fig. I), shows to what a magnitude the larva of a medium-sized Frog may grow ; for 

 the old individuals are but little larger than our native Grey Frog. 



As to actual length, more than two-thirds of this larva is a temporary structure, 

 and belongs to the tail ; the bulbous fore part, below, is half pharyngeal and half 

 abdominal. 



Supposing a measurement by vertical lines across the length of the creature, the dis- 

 tance between the anal aperture and the occipital hinge is one-third the length of the 

 essential animal ; the single gill-openuig (left side) is at the middle ; and the eye-ball 

 two-fifths from the front. 



Altogether, the outlets and inlets to the essential animal oxejive : three azygous — the 

 oral, anal, and pharyngeal; and two paired, the narial ; these latter are above and behind 

 the upper lip, and are small and rounded : they open into the palate almost vertically. The 

 mouth is small but complicated (Plate 1, fig. 2), the upper labials (Plate 2, figs. 1, 2, ;/./.) 

 arching over the horse.shoe-sliaped lower labials (Plate 10, fig. 5, l.l.) and the small oral 

 passage opening being between the halves of the horseshoe : the skin over these labials 

 is fonned into a horny plate, and the plicce of the lips are developed into horny rasps. 



Much fibrous tissue — some watery, some strong and tough — encloses the skull and 

 the outworks ; above, the head is marked by a median, and a pair of lateral, ridges ; 

 the facial cartilages are spread out on each side and lie on a plane but little below that 

 of the cranial cavity (see Plate 2). 



The " chondrocranium " at this stage is one of the best for comparison with that of 



