DEVELOPMENT OF THE SKULL IN THE BATRACHIA. 
207 
as the one next to be described, viz.: the Tadpole of B. lentiginosus, whose legs were 
only a line long, and in which (see Plate 38, figs. 9, 10) the parasphenoid was 
beginning. There is a remarkable want of uniformity in the time as to which certain 
parts appear. 
From the root of the pedicle ( pd. ) to the quadrate condyle (q.) we have the 
generalised counterpart of the quadrate of the Sauropsida; the metapterygoid and 
quadrate regions (together) of the Osseous Fishes. 
The free mandible (ink.) is only a short, thick, ray, with a notched condyloid tract, 
like that of the “ ulna,” ending in an angular process, like the “ olecranon.” 
Another, much larger, cartilage is articulated to the side plate by a rounded 
condyle ; the hollow for it is under the orbitar process ( or.p ., hy.f.) : this is the stylo- 
cerato-hyal ( c.hy .), it is a flat phalangiform piece, enlarged both proximally and 
distally, and united to its fellow by simple cartilage. 
The succeeding arches (branchial) have all been removed, and will not be described. 
Over the curling, pointed, horns of the trabeculae there is a pair of semi-lunar 
cartilages—notched behind ; these are the upper labials (u. I, ) not divided into two 
pairs. 
Below, between the mandibles, there is another pair ( l.l .), arranged crescentically ; 
they unite with each other in the middle, and are scooped, above. 
Above, and below, these labials are covered with the serrated horny plates that form 
the primary dental apparatus or “ odontophore ” of the Tadpole, which vanishes away, 
or is moulted off, during metamorphosis. 
This skull is unlike enough to that of the adult Toad, and would be even if no 
investing bones appeared, nor any bony tracts in the endocranium ; the passage of 
the larval into the permanent skull has, however, in this group, already been 
described. I shall now compare this and the next together. 
59. (A) Tadpole of Bufo lentiginosus. —f- inch long ; hind legs, - L f 2 - inch long. Penekese 
Island, Mass., U.S. 
The skull of this Tadpole (Plate 38, figs. 9, 10) (which was the same length as 
the last) is nearly a third longer, but very little wider; its breadth is only three- 
fourths of its length, and not nearly equal to it, as in the last kind. 
The difference between this skull and the last, and of both of them from that of 
B. vulgaris, is very remarkable, showing that the variations in the adult do not arise 
out of a uniform larval “ modelthe species, even, begin to vary as soon as they are 
hatched. 
In this specimen the hind legs are apparent, the Tadpole is only f of an inch long, 
and both this and the last are smaller larvae than those of the Common Toad. 
In Pseudis (A), as we have seen, the legs have relatively less development, but the 
skull is largely ossified, and as large as a crown-piece, the whole length of the Tadpole 
being 10^ inches, and its tail 4 inches across (Plate 1, fig. 1). Here, the skull is 
