LEPUS, 393 



canines and molars) and thecodont (in sockets) teeth, 

 the bony palate formed of bony expansions of 

 the maxillae and palatines meeting in the middle 

 line, two occipital condyles upon the exoccipitals, the 

 suspension of the lower jaw by the squamosal, the single 

 bone of the lower jaw and the three auditory ossicles. 



The large size of the nasal chambers and nasal bones, 

 the incomplete ossification of some bones, such as maxillae 

 and occipitals, the confluence of orbit and temporal fossa, 

 and, above all, the character of the dentition, are features of 

 the order Rodentia^ whilst the presence of small second upper 

 incisors and other lesser features are characteristic of the 

 sub-order containing rabbits and hares. 



The cranium of the skate could be recognised as formed 

 of the cranium proper and the cartilages of the three 

 sense-capsules. , Similarly the bones of the rabbit's skull 

 can be correlated with the cranium proper and the sense- 

 capsules. 



The former are arranged more or less in rings around 

 the cranial cavity which facilitates their recognition. 



The occipital ring is the most posterior. In many skulls 

 it may be completely detached from the others. It is 

 formed of a supraoccipital, paired exoccipitals and a basi- 

 occipital. 



The sphenoid ring \s> formed of paired /^r/V/aZr above 

 (and a small interparietal)^ paired alisphenoids laterally and 

 a basisphenoid. 



The presphenoid ring has a pair of frontals above, a pair 

 of orbitosphenoids laterally and a presphenoid below. 



The ethmoid ring has a pair of nasals above, a mes- 

 ethmoid below, which lies between the two nasal chambers 

 and broadens out posteriorly to form the cribriform plate ^ 

 and a perforated bony septum between the cranial and 

 nasal cavities. 



The bones of the sense-capsules are closely united with 

 those of the cranium proper. The auditory bones lie 

 between the occipital and sphenoid rings. They consist 

 of a periotic containing the inner ear and produced into a 

 prominent mastoid process^ and the tympanic Y^hich is swollen 

 into a hollow auditory bulla and produced upwards there- 

 from as a bony auditory meatus. The eyes are embedded 



