167 
DEVELOPMENT OF THE SKULL IN THE BATRACHIA, 
4. The small girdle-bone. 
5. The definite prenasal with its lateral projections. 
6. The junction of the pedicle with the stylo-hyal. 
7. The absence of a distinct inter-stapedial. 
8. The absence of hypo-hyal lobes. 
9. The extreme delicacy and narrowness of the fronto-parietal bones ; this is repeated 
in the other investing bones, but not to the same extent. 
44 (continued).—(B) Acris Pickeringii. —Larva, 1 inch 2 lines long ; tail, f inch ; hind 
legs, ^ inch ; same locality. 
The adult of tins species is smaller than that of Camariolius, but its Tadpoles are 
larger by one half; this specimen is more metamorphosed than the larva of that 
minute Australian “ Oxydactyle Frog” (see Plate 15, figs. 6, 7). 
In this larva the chondrocranium (Plate 30, figs. 6, 7) is oval in outline, for the hind 
part of the suspensorial bands and the fore part of the auditory capsules project, and 
the quadrate condyles (q.c.) are drawn in towards the mid-fine. It has gone beyond 
the Petromyzine stage, for there are two bones, both of them axial and azygous : one 
intrinsic, the cephalostyle or rudimentary basioccipital (n.c.) ; and the other superficial, 
the parasphenoid ( pa.s .). The first vertebra (c.v 1 .) is drawn with the crown of its arch 
cut away; in it we see the ossifying neural arches, and the relatively huge notochord 
(nc.) becoming invested with a layer of bony deposit, principally on its upper surface 
(fig. 6). This is taking place in the mesoblastic sheath, and is two-horned in front. 
Entering the skull, the notochord suddenly becomes very small, reaches to the same 
transverse fine as the Gasserian ganglia (V.), and ends in a rounded pomt, which is 
twisted to the right hand. This styfiform apex of the notochord is invested—most 
above—with a deposit of bone, like that which in the vertebral region forms rudi¬ 
mentary “ centra.” The bony “ cephalostyle ” has already been described as existing in 
the adult. The occipital arch is fast finishing, for cartilage is breaking out, above, from 
the inner edges of each auditory capsule, and this has converted most of the membrane 
there into the same tissue. Also in front of the notochord there is a long inter- 
trabecular tract of new, small-celled cartilage (fig. 6, inside tr.), and the orbital walls 
are beginning to grow over as a super-cranial ( tegminal ) rudiment; this is especially 
seen in front. 
Between the narial passages (i.n.) the trabeculae have coalesced, converging for this 
purpose, but there is no appearance here of a distinct mesethmoidal rudiment. The 
trabeculae break free of each other again, to end as free, crescentic, decurved horns, 
from whose inner edge a crest is growing to fill up the re-entering angle between them. 
The nasal roofs are only beginning to chondrify, and with the eye-balls, were removed 
in making the dissection. The auditory capsules began to chondrify directly after 
the trabeculae and suspensoria, and are now highly developed ; then canals ( a.s.c ., 
h.s.c., p.s.c.) bulge largely, and the ampulla of the horizontal canal projects greatly. 
