THE SKELETAL SYSTEM 21 



tine bone posteriorly. The orbital process overlaps the 

 anteroventral portion of the frontal bone's orbital process. 

 It forms but a small part of the wall of the orbito-tem- 

 poral fossa. A pronounced longitudinal groove on the 

 floor of the fossa partly separates the orbital from the 

 alveolar process. 



Lacrimal Bone (Os Lacrimale) 



The lacrimal bone is a thin inconspicuous element, of 

 membranous origin, lying on the dorsomedial wall of the 

 infraorbital foramen. It is immediately below the bony 

 arch which connects the dorsal surface of the skull with 

 the lateral part of the maxillary bone's frontal process. 

 The bone is easily overlooked if its sutures are not ex- 

 posed by careful scraping. 



PrEM AXILLARY BoNE (PrEM AXILLA) 



The premaxillary bone, of membranous origin, forms 

 the anterior part of the upper jaw, and the lateral and 

 ventral walls of the front part of the nasal cavity. With 

 the nasal bone it surrounds the anterior nares. Its frontal 

 process is thrust dorsally between the nasal and maxillary 

 bones, extending caudally to the frontal bone. This pro- 

 cess is partially overlaid laterally by the maxillary bone. 

 On the ventral side the palatine process extends hori- 

 zontally across the roof of the mouth, surrounding the 

 anterior part of the prepalatine foramen and meeting 

 its fellow at a median suture. This suture extends back- 

 ward between the two maxillary, as well as between the 

 palatine bones. The premaxillary bears an enormous 

 incisor tooth. Carefully chip away the bone surrounding 

 this tooth, and note the size and shape of the alveolus. 

 The palatine process joins the palatine process of the 



