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TRANSACTIONS OF THE AMERICAN PHILOSOPHICAL SOCIETY 



even doubt the proposed homologization of the process! palatobasales laterales in the rep- 

 resentatives of two such widely divergent classes of fishes. 



In conclusion, it may be suspected that many of the embryonic characters of the 

 sturgeon neurocranium and branchiocranium instead of being reminiscent of far-off pre- 

 Palseozoic gnathostomes may rather be anticipatory of peculiar specializations of the 



E.x 



penser stur/o 



Fig. 20. A. Skull of larval sturgeon (after Wiedersheim), showing downward bending of anterior end of skull upon the ver- 

 tebral column. B. Skull of larval sturgeon (after W. K. Parker). 



adult. Here belong such points as the concrescence of many vertebral segments with the 

 occiput, the curious downward bending of the fore part of the skull upon the occipital por- 

 tion (Fig. 20), the lack of a sharp cranial flexure in the early stages, the presence of barbels, 

 the foreshadowing of the suctorial characters of the adult mouth, the peculiar features of the 

 immense hyomandibular and large symplectic, the loss of the true opercular and the sub- 

 stitution for it of an enlarged subopercular. 



