22 PROCEEDINGS OF THE ACADEMY OF [1889. 



their ossification, but here in our specimen each pterygoid proper 

 now consists in a well-pronounced subcylindrical cartilaginous rod- 

 let to some extent centrally ossified, which, on either hand, projects 

 out from behind the ossifying palatine of its own side. External 

 to either one of these we observe the continuation of the bone in its 

 'external pterygoid plate,' which is also in cartilage, and arises 

 both from the ali- and basisphenoidal regions. Neotoma cinerea, in 

 the skull of the adult, shows well how the pterygoids are finally 

 fashioned in bone at maturity, and if they represent the condition 

 for the genus, we find that the external plate in each is nearly hori- 

 zontal in position, and raised above the frontal and sphenoidal 

 regions; the sutural traces remain quite distinct; the "hamular 

 processes " have their extremities produced, and turned slightly 

 outwards, while these apophyses are not far apart mesially, nor do 

 their ends lack much of reaching the auditory bulla on either side, 

 where the Eustachian tube opens. 



Passing next to a palatine bone, we find it to be ossified to no in- 

 considerable extent, with the salient angles of its horizontal portion 

 rounded off, its borders being yet membranous, or in an imperfect 

 cartilaginous stroma, a tissue furnished by the epiblast during the 

 growth of the embryo, and now taking on ossification. 



The ''posterior palatine foramina" are easily found, while the 

 hinder margins of these bones unite to form the lower free edge of 

 the posterior bases. 



Having the most usual relations to the nasal septum and surround- 

 ing parts, the ascending lamina of a palatine is not so thoroughly 

 ossified as the horizontal portion of the bone ; and at this stage of 

 its growth, this embryo Neotoma may be said to have a cleft palate, 

 so wide are the medial sutures between the elements. 



Of the endocranium, and the development of the cartilage bones. 



To Professor Kitchen Parker are we indebted more than to any 

 other single writer since the dawn of anatomical science to the pres- 

 ent time for our knowledge of the morphology of the vertebrate 

 skull, and from his recent writings, the mammalian skull in partic- 

 ular. Under the influence of his never weary hand, has this, one of 

 the most difficult problems which man has ever investigated, grown 

 out into the light with all the beauty associated with the budding of 

 a complete flower. In reading his "Structure and Development 

 of the Skull in the Mammalia" one loses himself as though he were 



