470 



MANUAL OF ELEMENTARY ZOOLOGY 



The Proboscidea or Elephants are generally classed with 

 the ungulates. They have all the five toes. The 

 Eiep ants. ^ run ^ [ s a muscular extension of the nose, with 

 the nostrils at the end. The tusks are the two upper incisors 

 and are composed of solid dentine or ivory. There are 

 no canines, but the six grinding teeth are very large and 

 transversely ridged, and are developed one at a time, so that 



Fig. 349. — The left side of a dog's skull, from which the zygomatic 

 arch has been cut away. 



/is., Alisphenoid ; c, canine tooth ; e.a.m., external auditory meatus \fr., frontal ; 

 g.f., glenoid fossa; i., incisor teeth; i.o.f., infraorbital foramen ; j., jugal; 

 lac, lacrymal ; m.., molar teeth ; mx., maxilla ; no.., nasal ; o.c, occipital con- 

 dyle (on exoccipital bone); OS., orbitosphenoid ; pa., parietal ; pal., palatine ; 

 pnr., premolar teeth; piux., premaxilla ; pi., pterygoid ; s.o., supraoccipital 

 (with which is fused an interparietal) ; s<j., squamosal ; sut., line of dots marking 

 the suture between the jugal and squamosal on the removed zygomatic arch ; 

 t. , tympanic ; 1 1. -I' I., foramina for cranial nerves. 



there is a succession of them, each being replaced as it 

 wears out. The testes do not descend into scrotal sacs. 

 The Hyracoidea, usually placed near the Elephants, are little 

 rabbit-like animals found in Palestine and Africa. Ifvrax, 

 the " coney " of Scripture, is the best known example. 



begin to show at lour years, and arc fully cut at five years, when all 

 the permanent incisors ate level. Al six years all the incisors show the 

 central enamel as a complete ring, and in the fust pair the cement is 

 almost gone from within it. At eight years litis pair shows the dentine 

 as a yellow line — the "star." 



