SKELETON. 



33 



V. Skeleton. 



The skull is more or less strongly depressed, and 

 remarkable for the extremely large orbits and the 

 reduction in the number of elements. We have to 

 distinguish between the chondrocranium, or primitive 

 skull — consisting mainly of cartilage with a few ossified 

 parts, witli a large fontanelle or membranous space in 

 the interorbital region, and foramina for the exit of 

 the cranial nerves, — and the membrane hones, which 

 may be removed by maceration. 



The ossified parts of the chondrocranium, or cartilage 

 bones (Fig. 1 1), are the ethmoid or sphenethmoid, form- 

 ing a ring round the anterior part of the brain-case, the 



Fig. 11. 



Ohondroovanium oi Rana esculenta. 



A. Upper view, 

 c. Brain-case. 

 e. Ethmoid. 

 eo. Bxoccipital. 

 fe. Fontanelle. 

 /m. Foramen magnum. 

 fo. Optic foramen. 

 ft. Trigeminal foramen. 



Lower view. 



j. JugaL 



I. Lachrymal process. 



n. Nasal capsule. 

 pr. Prootic. 

 pt. Pterygoid branch. 

 sp. Suspensorium. 



(paired) prootic behind the orbit, the (paired) exoccipital 

 on each side of the foramen magnum, forming the 

 (paired) occipital condyle articulating with the first ver- 

 tebra, and a styliform jugal connecting the cartila- 

 ginous suspensorium of the mandible or the ossified 

 quadrate with the maxillary. 



