SKELETON. 85. 
reduced or even disappear, those remaining being connected by a one or two-jointed 
copula. 
The chondrocranium of the larval ANURA (Rana, fig. 86) differs considerably 
from that of other amphibia as well as from the adult conditions. Like all amphib- 
ians it is platybasic. The pterygoquadrate has, besides the normal otic and 
epipterygoid processes, a cranio-quadrate process connected with the nasal region; 
in front of which is the articulation of the lower jaw. In front of the cornua, are a 
pair of suprarostral cartilages and a similar pair of infrarostrals lie in front of the 
Fic. 86.—Chondrocranium of tadpole of Rana before the metamorphosis; after Gaupp. 
¢.,ant, anterior canal; cls, superior labial cartilage; cfr, cornu trabeculz; car, foramen for 
carotid; ext. c, external canal; fe, ethmoid fenestra; m, Meckel’s cartilage; pc, posterior 
canal; po, otic process of quadrate; pr. as.’ ascending process of quadrate; g, quad- 
rate; #m, tectum medialis; ttm, tenia tecti marginalis; tsyn, tectum synoticum; J-V, nerves 
and nerve exits. 
Meckelian, from which they are apparently derived. These four rostrals form a 
ring around the suctorial mouth and recall the labial cartilages of the elasmobranchs 
and the annular cartilage of the cyclostome mouth. 
At the time of metamorphosis the changes are great, and as the result is more 
like the chondrocranium of other amphibia, the larval condition must be regarded 
as adaptive rather than ancestral. The suprarostrals disappear and the jaw 
shifts the hinge back to the normal position, this being accompanied by the elon- 
gation of Meckel’s cartilage, an absorption of the ascending process and a folding 
of the pterygoquadrate bar. At the same time a pterygoid grows out in front to 
join an antorbital process from the cranium. A stapes develops and connects 
