312 report— 1846. 



although its ' annular part' is closed above by a transverse plate* instead of 

 by a vertical spine, of which, indeed, there remains hardly more vestige than 

 is presented by the tubercle or rudiment of the spinous process in the supra- 

 occipital of man. It must also be remembered, that the human supraoccipital 

 does retain to a certain extent the same function in relation to the attach- 

 ment of the proper vertebral muscles (splenii capitis, complexi, and the modi- 

 fied interspinals called ' recti capitis postici maj. et rnin.) as the succeeding 

 vertebral spines ; and combines this with the same place of completing, as 

 the key-stone, the neural arch ; although by reason of the more voluminously 

 developed segment of the neural axis protected by that arch the peripheral ele- 

 ment is chiefly modified for the acquisition of the required increase of space. 



Cuvier next proceeds to comment on Ok en's endeavour to represent the 

 basisphenoid and the two alisphenoids with the two parietals as forming a ver- 

 tebra : and he admits that there is some analogy, though this is much more 

 feeble than the differences. "The basisphenoid, having another function, 

 takes on a different form from the basioccipital, especially above, by virtue 

 of the posterior clinoid processes : and in the embryo it is composed not of 

 a single nucleus, but of twof ." With respect to the objection from the 

 modification of form alluded to, it may be remarked that the same element 

 in other vertebral segments of the body undergoes much greater change 

 of shape; the centrums of the lower cervical vertebras in many birds send down 

 two processes as well-marked as the ascending ones called ' clinoid ' in that 

 of the parietal vertebra, not to speak of the ' soc de charrue' of the coccy- 

 geal vertebrae of the bird, for example, without any difficulty having been felt 

 or expressed by Cuvier in their recognition as modified vertebral bodies, the 

 more essential characters of their general homology being as plainly retained 

 as in the case of the basisphenoid ; in its relation, e. g. to the neur- 

 apophyses and the support of the mesencephalon. With regard to the 

 objection from the two centres of development, if this be valid against the 

 general homology of the basisphenoid (6, fig. 25) as a vertebral centrum, it 

 equally tells against the body of the atlas (c), which, as Cuvier well knew, 

 was ossified sometimes from two, and sometimes from three centres £. And 

 I may further observe that, although Cuvier affirms the two ossific centres of 

 the basisphenoid to retain for a long time between them simple cartilages, 

 my observations bear out the accuracy of the remark of Kerkringius, (whose 

 figures Cuvier cites,) touching the " dua ossicula distincta" (tab. xxxiv. fig. 

 iii. c, c), viz. " quae celerrime in formam figurae apposita? K coalescunt " : 

 and the figure of the coalesced rudiments of the basisphenoid given by Kerkrin- 

 gius closely resembles the bilobed rudiment of the vertebral centrums in the 

 sacrum of the chick. 



Cuvier next objects to the neurapophysial character of the alisphenoids, 

 that the ' foramen ovale ' is rarely a notch, more often a complete hole. 



* " Les vertcbres. L'atlas est compose de six pieces, &c. — La premiere, a, est une lame 

 transverse qui fait le dos de la partie annulaire. Elle n'a qu'une crete a. peine sensible pour 

 toute apophyse epineuse." — Ossemens Fossiles, t. v. pt. ii. p. 95. 



t En avant du basilaire se trouve le corps du spheno'ide posterieur, aux cotes duquel ad- 

 herent les deux ailes temporales ou grandes ailes. On a aussi cherche arepresenter ces trois 

 pieces comme formant une vertebre avecles deux parietaux. II reste en effet encore quel que 

 analogie, mais beaucoup plus faible, tandis que les differences deviennent plus fortes. Le 

 corps du spheno'ide a bien Fair d'une repetition du basilaire, mais ayant une autre fonction il 

 prende aussi une autre forme, surtout en dessus,au moyen des apophyses clinoides posters eures ; 

 et dans les premiers temps du fcetus il n'est pas compose d'un seul noyau, mais de deux, qui 

 out long-temps entre eux de simples cartilages." — /. c. p. 712. 



% Lecons d'Auat. Coruparee, t. i. (1836) p. 174. Meckel has figured the variety of three 

 ossific centres in this element of the human atlas in the 1st vol. of his Archiv fiir die Phy. 

 siologie, taf. vi. fig. 1. 



