294 ILLINOIS ACADEMY OF SCIENCE 



satz" and ''Cartilago palatina" with reference to the 

 same structure. It may be remarked parenthetically, that 

 the terms palatine cartilage or palato-quadrate arch, 

 frequently applied to the pterygoquadrate is incorrect, 

 as it contains no palatal element, and no part of the pala- 

 tine bone is derived from it. 



In the development of the chondrocranium of Crypto- 

 branchus alleghaniensis, possibly a more primitive Uro- 

 dele, some light is shed upon the history of this antor- 

 bital process. In a larva, two weeks after hatching, when 

 the cristae trabeculorum are already well-developed 

 there is no evidence of a developing antorbital. Slightly 

 posterior, however, to the position of its probable appear- 

 ance, precartilage cells have formed in the surrounding 

 tissue, lateral to the trabecula; and these cells continue 

 posteriorly into the anterior end of the pterygoquadrate, 

 extending forward from the hinge of the lower jaw. In 

 a larva five weeks old, these procartilage cells have chon- 

 drified; the pterygoquadrate now reaches farther for- 

 ward, and unites to the side of the trabecula in the posi- 

 tion from which the antorbital process normally devel- 

 ops in other Urodeles. In this stage, there is no exten- 

 sion forward of a cartilage bar from the junction of the 

 pterygoid with the trabecula; but in a larva three 

 months after hatching, a small process reaches forward 

 from the end of the pterygoquadrate toward the nasal 

 capsule, and an antorbital process has assumed propor- 

 tions similar to that in Amblystoma. My oldest larva 

 of Cryptobranchus does not show any connection be- 

 tween the antorbital process and the nasal capsule ; it is 

 probable, however, that in a later stage these parts would 

 be united, for the nervous supply and the associated 

 cartilages are similar to those in Amblystoma. 



In no other Urodele, as far as I have been able to dis- 

 cover, with the single exception of the Siberian genus 

 Eanodon (Wiedersheim, 1876; fig. 69) is there a similar 

 connection of the pterygoquadrate with the anterior part 

 of the skull. In a larva of Spelerpes fuscus (Wieder- 

 sheim, 1876; fig. 108) there is a cartilage bar directed 

 posteriorly from the nasal capsule toward the pterygo- 



