206 



UNGULATA 



ORDER VII 



Family 15. Oavicornia Reichenow. Hollow-horned Ruminants.^ 



In both sexes, sometimes only in the male, skull with osseous appendages encased 



in horn- sheaths. Dentition: ' ' ' ■ Sometimes only two premolars present. 



3.1.3.3. J -t r 



Superior incisor and canine teeth absent. Cheek teeth selenodont, hrachyodont or 

 hypsodont. Carpus and tarsus as in the Cervico7-nia. Chief metapodials united into 

 a cannon hone, with sharp distal median keels ; lateral metapodials never complete, 

 frequently loholly atrophied. Lateral digits present or absent. 



In comparison with the Cervicornia, the Cavicornia are seen to be progressive 

 ruminants, in manifold respects highly specialised. In the skull, the facial 



axis is inclined down- 

 ward, while the cranial 

 axis is horizontal (Fig. 

 287). The unusual ex- 

 pansion of the frontal 

 bones, however, lends a 

 still more characteristic 

 appearance to the Cavi- 

 cornia. AVhile the 

 frontal region posterior 

 to the orbits forms the 

 larger portion of the 

 cranial roof, it presses 

 the much reduced pa- 

 rietal bones backward, 

 and in the most ex- 

 treme forms (Bos) these 

 are entirely brought 

 into the occipital sur- 

 face. AVith the expan- 

 sion of the frontals is 

 frequently united a con- 

 siderable extension of 

 Fi«- 28V. the frontal sinus. The 



Skull of a Hornless Sheep in median vertical section. 1/3. ^.S', Ali- nonoa^^oi■a^\ tioonA io ro 



sphenoid ; 6ft, basihyal ; -BO, basioccipital ; BS, basisphenoid ;«/, articular ^'^"^-^^i'^'i't;^ uibbue ih le- 



condyle of lower jaw ; o/i, ceratohyal ; cp, coronoid process of lower jaw ; placed bv air-Cells and 

 eh, epihyal ; ET, ethmo-turbinal ; Exo, exoccipital ; Ft; frontal ; ME, -i j- i 



mesethmoid ; MT, maxillo-turbinal ; Mx, maxilla ; Na, nasal ; OS, orbito- the irOUtal region ex- 



sphenoid; Pa parietal; Per, periotic ; PI, palatine; PMx, premaxilla ; y.\Y,U^ j, .-.nPiiTiiatiV rnn 



pp, paroccipital process ; PS, presphenoid ; Pt, pterygoid ; s, symphysis of "iuiuo a, piiouiuciuiu uuii 



lower jaw ; sh, stylohyal ; SO, supraoccipital ; th, thyrohyal ; Ty, styli- ditiou In the autelooe 

 form process of tympanic ; Ko, vomer. (After Flower.) . ' . .^ 



this peculiar formation 

 of the frontal zone may be traced step by step in its development. While 

 in certain gazelles the frontal bones are still furnished with osseous cancellated 

 tissue, as in the deer, in others larger or smaller air-cavities are present. 



As a rule in both sexes, more rarely only in the male, bony protuberances 



^ Rdtimeyer, Die Riiider der Tertiarepocbe. Abh. Schweiz. Palaeout. Ges., 1877-78. — Rodler 

 und Weitho/er, Die Wiederkiiuer der Fauna von Maraglia. Denkschr. K. Akad. Wiss. Wien, 

 1890. — Schlosser, M., Versuch einer Odontographie der Antilopen. Abh.K. Bayr. Akad. Wiss., 

 1903, p. 161. — Die fossileu Cavicornier der Insel Samos. Beitr. Palaout. Ost.-Ung., xvii., 1904. 



