632 
ME. W. K. PAEKEE ON THE STETJCTUEE AND 
The pointed end of Meckel’s cartilage is tied to the upper surface of the corresponding 
labial ; this shows no tendency to become cirrose*. 
On the Skull of Dactylethra. — Second Stage. Tadpole If inch long. 
The skull of the next Tadpole is more than one third bigger, and the length is 
greater in proportion to the breadth ; thus the large preauditory flap does not nearly 
reach the hyoid condyle. This relative, as well as real, elongation of the chondrocranium 
makes it less anomalous, and more easily comparable with that of the common kind. 
Below (Plate 57. fig. 2), the cephalic part of the notochord ( nc .) is less, and reaches 
a shorter distance between the auditory capsules. It is more completely embraced by 
the investing parachordals ( iv .) ; where they clasp it behind there is on each side a gland, 
the “ thymus ” (tm.g.), close behind the double passage for the ninth and tenth nerves 
(9, 10). Above (fig. 1), the parachordals have united so as to form a superoccipital 
region ( s.o .), which has a concave margin in front exactly over the end of the notochord. 
Where the parachordals are lost in the trabeculae (fig. 2, tr.), there the gently convex 
cartilage is translucent enough to show the brain through it. Above (fig. 1), the 
brain is seen to be roofed over behind the optic lobes (C 2 ), this hides the medulla 
oblongata. 
The sides of the “ great fontanelle ” are somewhat overhung behind by the auditory 
capsules, and in front by the ascending plate of the trabecula. The hemispheres (C l 4 ) 
show in front of them the olfactory lobes (C 1“), and from these the crura are seen, 
through the transparent cartilage, burrowing their way to the olfactory sacs ( ol .). The 
median ethmoidal space is much denser, from the cranial cavity onwards ; and a solid 
“mesethmoid” ( eth .) is seen near the nasal organs (ol.) growing transversely to each 
hypertrophied trabecula, and forwards between the nasal sacs ; this is the true 
perpendicular ethmoid, and when it has grown well forward, the fore part will be the 
septum nasi. Looking below (fig. 2) we see that the chondrified pituitary floor at the 
middle has become much narrower, and that from beneath the mid brain, halfway to 
the frontal wall, there is beneath a delicate style of bone, with a truncated hinder end ; 
this first hone is the parasphenoid ( pa.s .). Altogether the trabecular plates are nar- 
rower, although still convex above and concave below ; the notch running from the 
subocular fenestra (so.f.) to the pedicle (pd.) is much more distinct. The trabecular 
plate is suddenly narrowed close to the nasal sacs below (fig. 2) ; here crescentic 
“ subnasal alee ” ( sn.l .), which converge towards the narrowest part of the internasal 
plate, bulge with the overlying nasal sacs (ol.). In front of these sacs the suddenly 
* With regard to the probability of the existence of Teleostean fishes, related to the existing Siluroids, 
during the Devonian epoch (Huxley, Mem. Geol. Surv. Decade 10, p. 29) it may he suggested that the Silu- 
roids now existing may be the specialized Teleostean representatives of truly Ganoid fishes, having a similar 
form, and existing in that early time. If so, we have three isomorphic groups of flat-headed Ichthyopsida, 
namely, such forms as the ancient Pterichthys , the modern Clarias , and the larval stage of this almost extinct 
kind of Toad ( Dactylethra ). 
