DEVELOPMENT OF THE SKULL IN THE BATRACHIA. 
Ill 
This larval skull will be best described by comparing it with the next (Plate 22, 
figs. 6-9 with figs. 2-5) ; all these objects are shown as magnified five diameters ; the 
Tadpole of Calyptocephalus was fully one-third Larger than that of Cyclorhamphus, and 
in the latter the hind legs were four times ( relatively ) as long as in the former, and 
therefore it must have been somewhat more advanced in development, generally. 
Indeed, this will be seen by comparison of the figures; yet this is too slight to 
effect the general form and relations of the parts. 
The interauditory region, in this, is altogether narrower ; the interorbital much 
more uniform, not narrowing, forwards, half as much ; and the palato-suspensorial bars 
converge more. On the whole, however, these two skulls might easily be taken for 
those of two species of the same genus ; part for part, and process for process, there 
is a very close resemblance between the two. 
The notochord ( nc.) is still found between the halves of the basal plate; the 
occipital condyles (oc.c.) have the same form ; the ex-occipitals (e.o.) are more deve¬ 
loped, answering to the longer legs, and are seen beyond the twin nerve-passages 
(IX., X.). The hinder “tegmen” only runs half as far forwards, and is not fenestrate, 
whilst the fore “tegmen” is finished and the single fontanelle ( fo .) is a large evenly 
oval space, instead of being a smaller space, shaped like an oval leaf, with the stalk 
in front. The auditory capsules are not thrust so far out; they are naked, and show 
the canals ( a.s.c ., h.s.c., p.s.c.) through then diaphanous walls ; the spurs growing from 
the “ tegmen tympani ” are very similar ( t.tysp.c.) ; the stapes (st.) is like that of the 
next. 
The almost oblong interorbital region (fig. 7) is shorter, and scarcely bulges at 
all; its walls are perfect and run an edge over the roof, on which the bony “ wall 
plates ” lie. The front tegmen runs forward as a wedge-like mass, for it has coalesced 
with the more developed intertrabecular crest, and the “ lamina perpendieularis ” (p. e .) 
is now formed. The lateral ethmoidal wings ( al.e .), and the upgrowths of the tra¬ 
beculae, outside the emerging olfactory nerves (I.), have conspired with the median 
crest and the roof to finish the plaster model for the future “ girdle-bone.” The first 
rudiment of the septum nasi exists, now, merely as the foremost part of the inter¬ 
trabecula ; beyond this frail commissure of the paired bands the cornua trabeculae 
(' c.tr .) diverge, arching both outwards and downwards ; they are longer and narrower, 
and more diverged than in the next, making the lozenge-shaped interspace left by 
them and the upper labials ( u.l a .u.l b .) much wider. 
The palato-suspensorial arch (pd., p.pg., q.) shows its likeness and its unlikeness 
to that of the other species. The pedicle (pd. ) is longer and the otic process is not 
distinct from the rounded “ elbow ” of the cartilage, which is bent backwards more. 
This, with the gradual convergence of the main bars, makes the orbital space wider 
behind ; it is, also, shorter. The orbitar processes (or.p.) do not overlap so much as in 
the next, but keep outside the post-palatine rudiment ( pt.pa .); this crest fails in its 
* In fig. 6 this is wrongly lettered t.cr. 
