DEVELOPMENT OF THE SKULL IN THE BATRACHIA. 
159 
three tracts of bone, as in the young of Rana temporaria (Phil. Trans. 1871, Plate 8, 
fig. 7, eth.). 
The broad end of the egg-shaped fontanelle (Jo.) is bounded by a very narrow 
tegminal tract; this tract is ossified, at first, evidently, as in the young of Rana 
temporaria of the first autumn, by ossification of the fibrous investment, and then by 
some degree of endosteal deposit. In Dactylethra (Phil. Trans. 1876, Plate 59, fig. L, 
s.eth .) the ossified membranous tract is large and "f" _s haped, but it does not unite with 
the extensively ossified chondrocranium; but in the phaneroglossal Anura, any 
external bone there may be is soon lost in the deeper ossification. 
In this “dwarf” the superior marginal crescent of bone seems to have started in 
growth from symmetrical points, but of this I am not certain; it may have been single 
and median at first, and then have become partly sub-divided afterwards—a very 
common thing in this group. In this narrow ethmoidal girdle the “axils” are 
ossified (eth.), and their limited lateral tracts unite with the arch of bone above, 
inside the superorbital band. That band (s.oh.) is double, there is a narrow tract 
over the anterior angle of the orbital space, and a wider lobe projecting from the 
ethmoidal wing; these two are separated by a deep rounded notch. 
The true nasal region is altogether unossified; it is of a good size both in length 
and breadth. The septum (s.n.) narrows a little, forwards, from the perpendicular 
ethmoid, and ends in front in a shortish, rounded rostrum (figs. 6, 7, 9) ; this 
rostrum is margined by the nasal roofs, and the front of this region is sinuous, 
and retires considerably, right and left. The pro-rhinals (figs. 7 and 9, p.rh.) are 
smallish and falcate. The broad subnasal laminae (fig. 7, on each side of s.n.) grow 
out into ear-shaped angular processes. The external nostrils (e.n.) are as wide apart 
as in other “ Polypedatkhe; ” they are almost as far apart as the inner openings 
( i.n .); the valvular cartilages (u.l l .u.l 2 .) are normal. 
The palato-suspensorial arches are normal, but feeble, so also are the bony tracts 
applied to them ( pa., pg.); both the hinder forks ( pd., q.c.) are short, and the quad¬ 
rate is not ossified. 
The Eustachian openings (eu. ) are nearly circular: they are two-thirds the size of 
the inner nostrils; the annulus (figs. 6, 10, a.ty.) is rather small, and imperfect above. 
The mandible (not figured) is normal, but feeble; the stapes (fig. 10, st.) is nearly 
semicircular, and has a long “ bossthe inter-stapedial is not cut off from the dilated 
and forked end of the stout arcuate medio-stapedial (■ m.st .), but is a massive, emar- 
ginate lobe of cartilage. The extra-stapedial (e.st.) is the short unossified end of 
this non-segmented columella; it is an inverted saddle-shaped process, and has no 
ascending ray. This small “ key ” is embedded in a thick cushion of fibrous and 
fatty tissue. The stylo-liyal end of the rest of the hyoid arch is not coalesced 
above; the descending bar (fig. 8, c.hy.) is of the normal width for the greater part 
of its length, but widens before it turns back into the hypo-hyal region ( h.hy.); this 
part has no front lobe, but on its outer side there is a small oval “ extra-hyal ” 
