34 
MR, W. K. PARKER ON THE STRUCTURE AND 
A remnant of the notochord ( nc.) still persists ; it lies on a thin junctional tract of 
the investing mass through which it is very visible. 
The fronto-parietals (fp.) are but little changed, and are not yet segmented. The 
parasphenoid ( pci.s .) has enlarged in its basi-temporal wings, in correspondence with 
the enlarging ear-capsules. 
There is only a stapes in the middle ear; no epi-hyal element has appeared. 
In accordance with the out-turning of the quadrate cond}des, the lower jaws (fig. 7, 
ink.) are longer; but the whole arch is largely extended by the strangely altered form 
of the original suctorial “horseshoe” formed by the “lower labials” (l.l.). Now, they 
are nearly straight, and stand across between the ventral ends of the mandibles. 
These latter bars are invested on their inner and lower face by the rudimentary 
“ articulare ” (or.). The maxillaries (rnx.) also have appeared above. 
Sixth Stage .—3. Half metamorphosed larva of liana-? sp. (India); If inch long; 
tail, f inch ; all. the legs free. 
The less important specific modification here seen (Plate 4, figs. 8-10) is the flat, 
wide cranium; the more important morphological changes are self-evident. The 
transversely extended auditory masses, and the wide flat occipital arch, are now largely 
becoming ossified by the two pairs of perineural centres ( pr.o ., e.o.) that gradually 
more or less occupy the occipital, periotic, and post-sphenoidal regions, protecting those 
parts of the head where the 5th to the 10th nerves emerge. The rest of the cranial 
“ barge ” is well chondrified, but has no bone as yet; the roof bones (f p.) are still 
large; the floor bone ( pci.s.) is a short, blunt, dagger, with a very wide “guard,” 
and a very short handle. 
Over the nasal roof the nasal bones (n.) are now crescentic shells of bone; the pre- 
maxillaries and maxillaries (px ., mx.) are now well developed, but the vomers are not 
apparent. A thin squamosal ( sq.) like a “ pre-operculum ” runs down the suspensorium, 
and the dentary (fig. 10, cl.) has appeared on the outside of the mandible, distally ; 
the coalesced “ lower labial ” is becoming ossified, and the dentary is grafting itself 
upon the endosteal patch, so as to form the “ mento-Meckelian bone the “ articulare ” 
(ar.) is lengthening with the jaw. 
The fore parts of the trabecula), now completely confluent with the nasal roofs, are 
broken up into a remarkable cervicorn structure. The inner angle of each is now the 
finger shaped, curved “pro-rhinal” (p.rh.), and the outer angle, which finishes the 
nasal floor in front, is divided into three lobes, one upper and two lower, that turn 
outwards, and are imbedded in the fore end of the maxillary. The two pairs of upper 
labials (u.l l .ud~.) are quite normal now, perfecting the antero-external edge of the 
nostril (fig. 8). Behind the pro-rhinals a pair of “ fenestra) ” (fig. 9, n.n.) are seen. 
The “pre-palatine” ( pr.pa.) has now escaped far away from the trabecular angle in 
fr< nt; it is a sharp falcate process at the fore end of a narrow band of cartilage which 
runs backwards until it is now opposite the prootic bone; there it ends in the suspen¬ 
sorium, which has become a stunted, triradiate cartilage, one-third of its former length. 
