AMPHIBIA 



I. Study of the skull of the bullfrog. 



(a). The skull of the frog, as in Amphibia generally, is broad 

 and flat. It is composed of four divisions: The 

 cranium or bones which surround the brain; the 

 auditory capsules which lodge the internal ears; the 

 olfactory capsules developed about the organs of smell ; 

 the jaws and hyoid apparatus. 



(b) . Identify the following bones : 



(i). The exoccipital bones are two irregular masses 

 forming the caudal boundary of the cranial 

 cavity. They boimd the foramen magnum, 

 through which passes the spinal cord, and 

 articulate with the first vertebra by means of 

 the occipital condyles, two oval convex 

 processes. 



(2) . The fronto-parietals are two long flat bones, one 

 on either side of the mesal line of the dorsum 

 of the skull. They form the roof of the 

 cranial cavity and are united at the meson. 

 Caudad they articulate with the exoccipitals 

 and prootics; cephalad with the spheneth- 

 moid which they overlap. The lateral 

 margins of the bones dip down into the orbits. 



(3 ) . The parasphenoid is a single bone on the ventral 

 side of the skull forming the floor of the 

 cranial cavity. It is cruciform in shape. 

 The cephalic arm, which is longest, extends 

 to and articulates with the palatines and 

 overlaps the sphenethmoid. The transverse 

 arms lie on the ventral surface of the exoc- 

 cipitals and prootics. The caudal arm is 

 short and triangular in shape. 



(4). The sphenethmoid forms the cephalic boundary 

 of the cranial cavity. It is overlapped by 

 the fronto-parietals and nasals from above 

 and by the parasphenoid and palatines 

 below. 



(s) . The nasals are triangular bones on the cephalo- 

 dorsal part of the skull. The cephalic por- 



