OF THE VENOM OF THE RATTLESNAKE. 7 



A second looks forwards and outwards. This facet is smooth below,' but is exca- 

 vated above into a deep fossa, which in the fresh snake is partially closed by 



Fig. 1. 



N/ 



Portion of Cranidm of Ckotalds.— Right side. Osteology. Boiies coucerued in the movements of the fang, a, 

 external pterygoid bone ; b, internal pterygoid bone ; c, palatal bone ; <i, superior maxillary bone ; e, lachrymal 

 bone. 



soft tissues, but is still sufficiently remarkable as lying between the eye and nares. 

 In the dry bone this large fossa opens upwards freely through the base of the bone, 

 and thus separates the two surfaces by which the bone articulates with the ecto- 

 pterygoid and lachrymal bones respectively. Anteriorly, the superior maxillary 

 bone presents a rounded angle, from which diverge the two lateral sides just 

 described. Posteriorly, the superior maxillary exhibits a third face, which is flat 

 only half way down the bone, and terminates in an abrupt edge forming the poste- 

 rior boundary of the alveolar socket. 



Anteriorly, and above, the maxillary bone articulates by a ginglymoid joint with 

 the short triangular lachrymal bone. Fig. 1, e, which projects forwards from the 

 anterior external angle of the frontal bone. The articular facet of the maxilla lies 

 at the upper end of its front angle. It moves with great freedom on the concave 

 face of the lachrymal bone, its motion being partially restrained by a short, round, 

 strong ligament, which runs from the posterior and inner edge of the lachrymal 

 bone to be inserted on the back edge of the base of the maxilla, just above the 

 articulation of the ecto-pterygoid bone. 



The lachrymal bone has itself some movement on its frontal articulation, and by 

 this the maxilla obtains indirectly an additional extent of forward motion. At the 

 upper edge of the posterior surface of the maxillary bone, it receives the expanded 

 and flattened end of the ecto-pterygoid bone. Fig. 1, a. Upon tracing the line of 

 motion, of which this bone is capable, it will be seen that it lies below the lachrymal 

 joint, and that, consequently, when it moves forwards, the fang must rise, as the 

 superior maxillary rocks on the articulating flice of the lachrymal bone. 



The superior maxillary is indirectly attached to the palate bone, Fig. 1, c, and 

 internal pterygoid. Fig. 1, b, by virtue of the strong connection of these bones with 

 the ecto-pterygoid. This connection is so close that every free motion of either of 



The parts are described as though in situ. 



