122 BULLETIN OF THE ESSEX INSTITUTE. 



But more important than any of the features mentioned 

 above is the existence of an isolated palatine cartilage. 

 This is especially noteworthy since it seems to furnish 

 strong evidence in opposition to the theory of the Uro- 

 delan ancestry of the Csecilians. Ranodon is the only 

 Urodele which possesses that portion of the palato-ptery- 

 goid arch which may be considered to correspond to the 

 palatine cartilage of Ichthyophis, while in Amphiuma 

 there is not the slightest trace of it. We may therefore 

 conclude that the condition found in Ichthyophis was not 

 derived from an Urodelan ancestor but from some more 

 primitive form. 



The articular process of Meckel's cartilage is unusually 

 long in Ichthyophis. The nasal capsules, while differing 

 from all the others described, have no features of sufficient 

 importance to be of any especial classificatory value. 



The evidence which I have found, chiefly from a study 

 of the chondrocranium, appears to me to be against asso- 

 ciating the Caecilians with any of the Urodeles and in favor 

 of keeping them in a distinct group coordinate with the 

 Urodela and Anura. 



POLYPTERUS BICHIR (Fig. 27). 



In 1892 the late H. B. Pollard kindly allowed Dr. 

 Kingsley to trace the outlines of the cartilages in the 

 sections of the head of his youngest Polypterus. From 

 these drawings I have made the chondrocranium in wax. 

 Since the skull of this same specimen has already been 

 described and figured by Pollard ('91) I shall deal 

 chiefly with points of value from a comparative stand- 

 point. For further details in regard to the relations of 

 the chondrocranium to the rest of the head, reference 

 should be made to Pollard's paper Avhich contains a 



