DEVELOPMENT OF THE SKULL IN THE BATRACHIA. 91. 
The extra-branchials ( ex.br A 4 ) are quite normal, and each has its own cerato- 
branchial rudiment ( c.brP 4 ) coalesced below with it. 
The fronto-parietals (fig. 1 ,fp.) are small blades of bone, pointed in front, broader 
behind, and resting on the roof-edge of the skull. 
The parasphenoid (fig. 2, pa.s.) is very noticeable; it is U-shaped, and half cleft into 
two pieces; this character attains in this, and in its congeneric larva, to an extent not 
seen by me in any other type of the “ Ichthyopsidaa front notch is seen in every 
stage of Pseudis, but it is small. 
Most of the cranial nerves (fig. 2, II., V 1 ., V 2,3 ., VII., VII'., IX., X.) are shown 
issuing from their foramina, as in the last kind of larva. 
19 (continued).—(B) Cystignatlius ocellatus (?).—Second larva; 3^ inches long; tail, 
2^ inches ; hind legs, 1 line long. Brazils. 
In development, this Tadpole corresponds very exactly with my huge youngest larva 
of Pseudis (Plates 1 and 2) ; the hinds legs are relatively of the same size and are at 
the same stage. 
The chondrocranium (Plate 17, figs. 5, 6) is one-half larger than the last, and certain 
changes have taken place in it of importance. The notochord (nc.) is shrinking, and 
the basal plate closing in upon it; the occipital condyles (oc.c.) are better formed, and 
the cranial cartilage has fused more completely with the auditory capsules. A dis- 
coidal exoccipital encloses the 9th and 10th nerve (e.o., IX., X.), and the prootic ( pr.o .) 
is beginning to creep up the front of the auditory capsule behind the foramen ovale. 
The canals of the ear ( a.s.c ., h.s.c., p.s.c .) are very clearly seen above ; below, the 
capsules are getting flattened sides, which lessen backwards ; in the side, under the 
large leafy tegmen tympani ( t.ty .) the fenestra ovalis has become almost vertical, and 
a nucleus of cartilage is now 7 to be seen in the soft plug of tissue that fills it; this is 
the stapes (fig. 6, st.). The tegmen tympani is elegantly angulated behind ; in front 
it is continuous with the spiracular cartilage ( sp.c .), a large sub-falcate flap, which has 
coalesced also now with the budding “otic process” ( ot.p .). The interorbital region 
of the skull is more perfect, but of the same shape ; the pear-shaped fontanelle (fo.) 
is widest, now, further back, and the front tegmen is more solid, and has united with 
the trabecular edges and hidden median cartilage to finish the ethmoidal region. 
The olfactory nerves (I.) are seen emerging, but the nasal roofs are still membranous, 
and were removed in the preparation. Yet the intertrabecula is filling in the space 
between the trabeculae up to the membranous margin of the internal nostrils ( i.n .). 
That membrane, however, has in it no spur growing from the trabecular cornu ( c.tr .), 
which is narrowed further forwards than in the last stage ; for the rest, these, and the 
upper labials ( u.l a .u.l b .), are only larger. The pedicle of the palato-suspensorial arch 
(pd.) is less transverse; the orbitar process ( or.p .) is further out; the post-palatine 
rudiment ( pt.pa.) is now fairly differentiated from the ethmoidal wing ( cd.e .), now 
n 2 
