8 THE NECTURUS 



BONES OF THE SKULL 



By boiling the skull of the specimen used for dissection 

 a very good disarticulated skull can be obtained. Boil for 

 half an hour in a mixture of soap, ammonia and borax. 

 Separate the bones, one at a time so as to be sure of the 

 relations. It is better to use the left side for the dis- 

 articulation thus keeping the right side intact for com- 

 parison. It will be necessary to use a safety razor to spUt 

 the parasphenoid. 



The following bones do not appear in the skull of Nec- 

 turus; maxilla, occipitals, the maxilla is lost entirely, the 

 occipitals are not ossified, and the palatines have joined 

 with the pterygoids to form the palato-pterygoids. 



Premaxilla 

 The premaxilla is a V shaped bone at the anterior end 

 of the skull. Its inner limb rests on the frontal, which is 

 its only articulation with the other bones. The exterior 

 limb of the V is free and extends posteriorly along the 

 vomer. The underside of the free limb is supplied with a 

 number of conical teeth. 



Vomer 

 The vomer is a flat, triangular bone forming a part of 

 the upper jaw. The outer region of the ventral face bears 

 a ridge upon which are numerous fine teeth. Most of the 

 teeth of the upper jaw region are on this bone. There is 

 an articulation between the vomers. Besides this they 

 articulate with the parasphenoid, and palatoquadrate. 

 The dorsal side of the bone bears an elevated ridge that ex- 

 tends dorsally and articulates with the frontal. 



Palato-pterygoid 

 This combined bone is long, thin and somewhat 

 rectangular in shape. It connects the vomers and the 



