24 ^^y- [Vol. IV. 



The ulna and radius, carpal, metacarpal, and phalangeal ele- 

 ments are present in cartilage. 



The pelvic girdle consists of a plate of imperfectly differen- 

 tiated cartilage on each side, which has no connection with the 

 vertebral column above nor with its fellow below. Femur, 

 tibia, and fibula are present in cartilage, as well as some portions 

 of the foot. 



IV. Observations on a Larger Specimen. 



Since the above was written, I have received from the collec- 

 tions of the United States National Museum a specimen of 

 AvipJiiinna six inches long, one of the smallest in the collection. 

 This has been secured in the hope that it might throw some 

 light on the origin of certain structures which had not yet made 

 their appearance in the very young, and might furnish, in the 

 case of other structures, stages intermediate in development 

 between those of the already described larva and those of the 

 adult. Of such structures the most interesting, perhaps, are 

 the unpaired piece of cartilage which is found in the roof of the 

 mouth, and the various portions of the premaxillary bone. The 

 specimen has been decalcified, stained, cut, and mounted seri- 

 ally; and such results as I have been able to obtain are now 

 presented. 



As might have been anticipated, this specimen is already too 

 far advanced in development to be of the highest value for the 

 solution of the problems before us. The skull is nearly as 

 thoroughly ossified as it is in the adult. Nevertheless, the prep- 

 aration is, I think, a very instructive one. 



An examination shows that the cartilage which was found in 

 the hinder part of the floor of the brain-case of the unhatched 

 larva has been extensively removed, so that there is now none 

 of this tissue in the middle line between the ethmoidal plate 

 and the narrow basioccipital cartilage. The base of the skull, 

 therefore, as regards the primordial elements, is much like that 

 of Necturus, except that such cartilage as remains along the 

 borders of the otic capsules is more extensively ossified in the 

 A^nphhnna. In the region about the anterior end of the pro- 

 otic, where in the larva a band of cartilage is sent from side to 

 side, a shelf of bone, now a process of the prootic, extends in- 



