THE CHONDROCRANIUM IN THE ICHTHYOPSIDA. 133 



capsule and an outer incomplete osseous case, to which, 

 again, some other cartilaginous elements are appended." 

 From this description and from the fact that a cartilage 

 considered to be a remnant of the hyomandihular has 

 been found in Ceratodus it seems prol^able that the chon- 

 drocranium of this form resembles that of the Fishes more 

 than does that of Protopterus. But the evidence from the 

 chondrocranium of Protopterus, in so far as it may be con- 

 sidered to have value in determining the position of the 

 Dipnoi as a whole, appears to me to be entirely in agree- 

 ment with the conclusion of W. N. Parker that, " it is 

 certainly inadvisable to retain the Dipnoi among the 

 Fishes, as is still done by some zoologists, and it would 

 be still more undesirable to place them with the Amphi- 

 bia." It is to be remembered, however, that Protopterus 

 is one of the more specialized forms of the group. 



Postscript. 



Since the foregoing article passed into the hands of the 

 printer a paper by Miss Platt^ has appeared which deals 

 with the development of the cartilaginous skull of Nectu- 

 rus, giving special attention to the origin of the procar- 

 tilage cells. In the main our results in regard to the fully 

 chondritied parts entirely agree. Miss Piatt finds, how- 

 ever, that in Necturus the number of cartilages arising 

 independently is considerably larger than that desonl)ed 

 above for Amblystoma. Of these the synotic tectum 

 ('tectum interoccipitale'), the trabecular crest, and the 

 ethmoid ('internasal ') plate are of particular interest 



■ Piatt, J. B. The development of the cartilaginous skull and of the brauchlal 

 and hypoglossal musculature In Necturus. Morph. Jahrbuch. xxv, p. :fJT. 1897. 



