DEVELOPMENT OF THE SKULL IN THE BATRACHIA. 
89 
1. The small size of the ex-occipitals and prootics. 
2. No girdle-bone. 
3. The fontanelle single and largely uncovered. 
4. The evident outlines of the elements composing the nasal region. 
5. The presence of a prenasal rostrum. 
6. The articulation of the ethmo-palatines with the ethmoid above. 
7. The rudimentary condition of the annulus and columella. 
8. The arrested state of the mandible and simple condition of the hyo-branchial 
structures. 
9. The absence of teeth on the vomers. 
Third genus. Cystignathus. 
19. (A) Cystignathus oceilatus (?).—First larva. Brazils.* 
First larva ; inches long ; tail 1-| inch.; hind legs not visible. 
This is the most immature of the Batrachian larvm of which I have as yet given 
illustrations in this memoir; I have already referred the reader to much earlier stages, 
figured and described in my published papers. 
These skulls are relatively very solid, and what strikes the eye at once is their 
oblong form and the straightness and width of the cornua trabeculae. The chondro- 
cranium (Plate 17, figs. 1, 2) is quite complete, and it has passed from the simple 
primary condition by having had three osseous tracts applied to its surface ( fp.,pa.s .), 
Except for the projecting cornua and labials, the skull up to the quadrate condyles 
(q.c.) is very evenly oblong, and only one-tenth longer than broad. The occipital con¬ 
dyles (oc.c. ) project but little beyond the auditory swellings; the halves of the basal 
plate are separated by a considerable notochord ( nc .), and the cartilage which unites 
the basal plates with the periotic capsules is young and crowded with corpuscles. 
The tegmen cranii, both fore and aft, is also made of young cartilage, and its 
boundaries are traceable; it leaves one large fontanelle (fo.), which is pyriform in 
outline, with the stalk behind. Up to the middle of the internal nostrils (i.n.) the 
intertrabecular plate has conjugated the trabeculae (tr.) ; from thence the massive 
cornua (c. tr.) diverge gently. Behind, the canals of the ear (fig. 1, a.s.c., h.s.c., p.s.c.) 
* These were taken with the species here named, and presumably belonging to it, from Rodsio (a tributary 
of Rio des Macacos) above the Falls, Brazils, May, 1865 ; they are the gift of Prof. A. Agassiz. I shall 
treat of these as belonging to the type named, with the above explanation, as also the skull of another, 
much smaller larva, with no title, but only the locality from which it was taken, namely, Lake 
Jannarg, Manaoo, Brazils. Whichever genus the larger Tadpoles belong to, to that also the little larva 
belongs; these two species have larval skulls very distinct from what is seen in Rana, Calyptocephalus, 
Cyclorhamphvs , the Hylidae, or the species of Bufo; they are most like those of the earlier stages of 
Pseudis. Merely as a study of a variety of the larval Batrachian skull they are very valuable; and I trust 
that some friend will verify their title for me, and if there be any error, correct it. 
MDCCGLXXXI. N 
