112 SKULL OF THE CROCODILE. 



illary, 25, the malar, 26, and the postfrontal, 12. The 

 second diverging ray is of great strength; it extends from 

 the maxillary, 21 ("hsemapophysis" of the maxillary arch), 

 to the tympanic, 28 (" pleurapophyses" of the mandibular 

 arch), and is divided into two pieces, the malar, 26, and 

 the squamosal, 27. Such are the chief crocodilian modi- 

 fications of the haemal arch, and appendages of the ante- 

 rior or nasal vertebra of the skull. 



The haemal arch of the frontal vertebra is somewhat less 

 metamorphosed, and has no diverging appendage. It is 

 slightly displaced backwards, and is articulated by only a 

 small proportion of its pleurapophysis, 28, to the parapo- 

 physis, 12, of its own segment; the major part of that 

 short and strong rib articulating with the parapophysis, 

 8, of the succeeding segment. The bone, 28, called "tym- 

 panic," because it serves to support the " drum of the ear" 

 in air-breathing vertebrates, is short, strong, and immov- 

 ably wedged, in the crocodilia, between the par occipital, 

 4, mastoid, 8, postfrontal, 12, and squamosal, 27 ; and the 

 conditions of this fixation of the pleurapophysis are ex- 

 emplified in the great development of the ha3mapophysis 

 (mandible), which is here unusually long, supports numer- 

 ous teeth, and requires, therefore, a firm point of suspen- 

 sion, in the violent actions to which the jaws are put in 

 retaining and overcoming the struggles of a powerful 

 living prey. The movable articulation between the pleu- 

 rapophysis, 28, and the rest of the haemal arch is analogous 

 to that which we find between the thoracic pleurapophysis 

 and hsemapophysis in the ostrich and many other birds. 

 But the haemopophysis of the mandibular arch in the 

 crocodiles is subdivided into several pieces, in order to 

 combine the greatest elasticity and strength with a not 

 excessive weight of bone. The different pieces of this 



