907 



" (c.) Shows the bony arch thrown over the mouth of the cavity, and dividing that into 

 two openings, which give origin to the two fangs. 



" (d> e,f.) Show the progress of these fangs." Op. rit. pi. xiii. fig. 1. A, a, B, C, 

 D, E. 



5875. (Slide, Div. 20.) Five specimens of the first true molar of the upper jaw, 

 similarly displayed. 



" (g.) Shows the common cavity of the tooth. 



" (A.) Shows the slight tucking in of the mouth of the cavity, at three different points, 

 from which three ossifications shoot. 



" (t.) Shows these ossifications, and the beginning of three fangs. 



"(k, 1.) Show the gradual growth of these fangs." Op. eit. pi. xiii. fig. 1. A, a, F, G, 

 H, I, K. 



5876. A premolar or 'bicuspid,' longitudinally bisected, of a Man. 



Presented by Sir Everard Home, Sort., F.R.S. 



The following specimens, to No. 5885 inclusive, exhibit the relations of the Human 

 skeleton to the archetype of the Vertebrate skeleton : 



5877. The first dorsal segment of the skeleton of a Human Foetus. 



It shows : c, the centrum ; n, the neurapophyses ; pi, the pleurapophyses ; hi, the haemal 

 spine, all distinct elements of the segment at this period : the hsemapophyses are unossified. 



Presented by Prof '. Owen, F.E.S. 



5878. The sixth cervical segment of the same skeleton. 



It shows : c, the centrum ; n, the neurapophyses, and pi, the pleurapophyses. That of 

 the right side is left in its natural connections with the diapophysial process of the neurapo- 

 physis : it is a slender, short bony bar, thickest at its outer end ; it forms the lower boundary 

 of the canal for the vertebral artery, and when coalesced, the pleurapophysial part of the 

 transverse process. 



Presented by Prof. Owen, F.E.S. 



5879. The last two dorsal, with the lumbar and sacral segments, or vertebrae, of the 

 same skeleton. 



The pleurapophyses of the eleventh and twelfth dorsals are ossified. The diapophyses of 

 the lumbar vertebrae show the same well-defined terminal flattened surface, as those of the 

 dorsals for the costal articulation, but only the cartilaginous bases of the pleurapophyses hare 

 been preserved. In the first and second sacral vertebrae, a distinct osseous centre has oeen 

 established in the cartilaginous basis of the pleurapophysis, which occupies the same relative 

 position as in the cervical vertebrae : these costal elements are, however, much thicker in 



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