98 BRITISH FOSSIL REPTILES. 



presently to be described, PI. 1 A, fig. 1, differs from all the modern species, in the 

 exclusion of the nasal bones (i.i) from the nasal aperture. 



Both the palatine (fig. 13, 20) and the maxillary (ib. 21) send outwards and back- 

 wards, parts or processes which diverge from the line of the haemal arch of which they 

 are the chief elements ; and these parts give attachment to distinct bones which form 

 the ' diverging appendages' of the arch, and serve to attach it, as do the diverging 

 appendages of the thoracic haemal arches in the bird, to the succeeding arch. 



The appendage (24) called ' pterygoid' effects a more extensive attachment, and is 

 peculiarly developed in the CrocodiUa. As it extends backwards it expands, unites with 

 its fellow, below the nasal canal, and encompassing that canal, coalesces above it with 

 the vomer, and is firmly attached by suture to the presphenoid and basisphenoid : it 

 surrounds the hinder or palatal nostril, and, extending outwards, as shown in PI. 1 A, 

 fig. 3 (24), it gives attachment to a second bone (25), called ' ectopter}'goid,' which is 

 firmly connected with the maxillary (25), the malar (26), and the post-frontal (12). The 

 second diverging ray is of great strength ; it extends from the maxillary (21) (' haema- 

 pophysis' 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 modifications of the haemal arch and appendages of the 

 anterior 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 parapophysis (12) of its own 

 segpient ; the major part of that short and strong rib articulating with the para- 

 pophysis (8) of the succeeding segment. The bone (28) called ' tympanic,' because it 

 serves to support the ' drum of the ear,' in air-breathing vertebrates, is short, strong, 

 and imraoveably wedged, in the CrocodiUa, between the paroccipital (4), mastoid (s), 

 post-frontal (12), and squamosal (27); and the conditions of this fixation of the pleura- 

 pophysis are exemplified in the great development of the haemapophysis (mandible), 

 which is here unusually long, supports numerous teeth, and requires, therefore, a firm 

 point of suspension, in the violent actions to which the jaws are put in retaining and 

 overcoming the struggles of a powerful living prey. The moveable articulation 

 between the pleurapophysis (28) and the rest of the haemal arch is analogous to that 

 which we find between the thoracic pleurapophysis and haemapophysis in the Ostrich 

 and many other birds. But the haemapophysis 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 purposely sub- 

 divided element have received definite names. That numbered 29, which offers the 

 articular concavity to the convex condyle of the tympanic (28), is called the ' articular' 

 piece ; that beneath it (30), which dcvelopes the angle of the jaw, when this projects, 

 is the ' angular' piece ; the piece above (29') is the ' surangular ;' the thin, broad, flat 



