CHOCODILIA. 



95 



Fig. 12. 



for the ribs or haemal arches of their respective vertebrae ; and these characters are 

 retained in the postfrontals as well as in the mastoids of the Crocodiles. 



The frontal parapophysis ( 12, fig. U) is wedged between the back part of the spine 

 (ll) and the neurapophysis (lo) ; its outwardly projecting process extends also back- 

 wards and joins that of the succeeding parapophysis (s) ; but, notwithstanding the 

 retrogradation of the inferior arch (fig. 13, H iii), it still articulates with part of its 

 own pleurapophysial element (28), which forms the proximal element of that arch. 



There finally remain in the cranium* of the Crocodile, after the successive detach- 

 ment of the foregoing arches, the bones intersected by the double line N iv, in fig. 13, 

 which, as in fig. 14, are numbered 13, U, and 15, and of which a foreshortened back view 

 is represented in Cut 12 ; but, notwithstanding the extreme degree of modification 

 to which their extreme position subjects them, we can still trace in their arrangement 

 a correspondence with the vertebrate type. 



A long and slender symmetrical grooved bone (i3, between 24, 24), like the ossified 

 inferior half of the capsule of the notochord, is con- 

 tinued forwards from the inferior part of the cen- 

 trum (y) of the frontal vertebra, and stands in the 

 relation of a centrum to the vertical plates of bone (14), 

 fig. 12, and fig. 14, which expand as they rise into a 

 broad, thick, triangular plate, with an exposed hori- 

 zontal superior surface. These bones, which are called 

 ' prefrontals,' stand in the relation of ' neurapophyses' 

 to the rhinencephalic prolongations of the brain, com- 

 monly but erroneously called ' olfactory nerves ;' and 

 they form the piers or haunches of a neural arch, which 

 is completed above by a pair of symmetrical bones (15) 

 called ' nasals,' which I regard as a divided or bifid 



neural spme. Disarticulated rhinencephalic arch, with 



The centrum of this arch is established by ossifi- the anchylosed pterygoids (24) in dotted 

 cation in the expanded anterior prolongation of the "'^^^'^^ (Crocodne). 

 fibrous capsule of the notochord, beyond the termination of its gelatinous axis. The 



* The part called cranium in human anatomy is a quite artificial division of the skull ; it includes the 

 neurapophyses of the nasal vertebrae, coalesced with the capsules of the sense of smell, and excludes the 

 centrum and neural arch of the same natural segment ; it also includes one portion of the diverging 

 appendage (27) of the maxillary arch, because it enters largely into the formation of the capacious cranial 

 cavity of man, and another portion of the diverging appendage of the same arch (24), because it happens to 

 coalesce with the basisphenoid. The capsule of the organ of hearing is included together with part of that 

 of the olfactory organ, whilst the capsule of the organ of sight, and part of that of the organ of smell are 

 excluded. None of these sense-capsules properly form any part of the cranium, but they are lodged in 

 interspaces of its constituent arches. The cranial portion of the skuU, as a natural division of that part 

 of the endoskeleton, ought to consist exclusively of the neural arches and centrums of the cranial vertebrae. 



