ANATOMY OF VERTEBRATES. 151 



maxillary bone : between these processes the palatine is perforated, 

 and behind them it terminates in a point. The chief part of the 

 maxillary bone, 21, is continued forward from its point of suspen- 

 sion, increasing in depth, and terminating obtusely : a shorter 

 process is also, as usual, continued backward. The point of 

 suspension of the maxillary forms a short, narrow, palatine process : 

 the dental branch of the supramaxillary nerve penetrates the 

 upper and fore part of this process, and its chief division escapes 

 by a foramen on the outer and fore part of the maxillary. A space 

 occupied by elastic ligament intervenes between the maxillary and 

 the premaxillary, 22, which is single and symmetrical, and firmly 

 wedged into the nasal interspace : the anterior expanded part of 

 this small triangular bone supports two teeth. Thus the bony 

 maxillary arch is interrupted by two ligamentous intervals at the 

 sides of the premaxillary key-bone, in functional relation to the 

 peculiar independent movements of the maxillary and palatine 

 bones required by Serpents during the act of engulfing their 

 usually large prey. 



Two bones extend backward as appendages to the maxillary 

 arch ; one is the e pterygoid,' 24, from the palatine, the other the 

 ectopterygoid, 25, from the maxillary. The pterygoid is continued 

 from the posterior extremity of the palatine to abut against the 

 end of the tympanic pedicle : the under part of its anterior half 

 is beset with teeth, fig. 96, 24. The ectopterygoid, 25, overlaps 

 the posterior end of the maxillary, and is articulated by its posterior 

 obliquely cut end to the outer surface of the middle expanded part 

 of the pterygoid. 



Mandibular arch. — The tympanic bone, 28, is a strong, trihedral 

 pedicle, articulated by an oblique upper surface to the end of the 

 mastoid, 8, and expanded transversely below to form the antero- 

 posteriorly convex, transversely concave, condyle for the lower jaw. 

 This consists chiefly of an articular 31, and a dentary 32, with a 

 small coronoid and splenial piece. The articular piece, 31, including 

 the angular and surano-ular elements of the Crocodile, ends ob- 

 tusely, immediately behind the condyle : it is a little contracted in 

 front of it, and gradually expands to its middle part, sends up two 

 short processes, then suddenly contracts and terminates in a point 

 wedged into the posterior and outer notch of the dentary piece. The 

 articular is deeply grooved above, and produced into a ridge below. 

 The coronoid is a short compressed plate : the splenial is a longer 

 plate applied to the inner side of the articular and dentary. The 

 outer side of the dentary has a single perforation near its anterior 

 end : this is united to that of the opposite ramus by elastic ligament. 



