1903.] THE MUSCLES OF THE UNGULATA. 291 



to the 6tli or 7th caudal vertebra, while the former runs to the 

 tip of the taiL 



The Tnterspinales and Intertransverscdes eaudce are feebly 

 developed and diminish as the bones decrease in size. 



Addendum. 



Orbital Muscles. — In addition to the recti and obliqui of human 

 anatomy, there is a retractor bulbi or posterior rectus which sur- 

 rounds the optic nerve and is inserted into the posterior part of 

 the eyeball. This in the Ohevrotain (20, 21) is divided into an 

 upper and lower part, while in the Horse (63) and Ass (69) the 

 division is more complete, for it is divided into four slips corre- 

 sponding to the four recti. In the Horse (63) and Ass (69) there is 

 also a middle oblique muscle which rises from the inner wall of the 

 orbit below the pulley and later on joins the superior oblique ; it 

 is apparently a part of this muscle which does not pass through 

 the pulley. We have looked for this muscle in the Artiodactyla 

 but have never seen it, nor do we know whether it occurs in the 

 Rhinoceros and Tapir among the Perissodactyla. 



General Summary. 



We now propose to consider whether a study of these muscles is 

 of any value from a classificatory point of view, and it will perhaps 

 be best to collect first those myological points which are common 

 to all Ungulates though not common to all mammals. 



Myological Characteristics of the Ungidata. 



1. Almost constant presence of masto-styloideus. 



2. Absence of epitrochleo-anconeus. 



3. Rudimentary condition of pronator radii teres. 



4. Absence of pronator quadratus (except in Tapir). 



5. Position and function of extensor carpi ulnar is as a flexor of 

 the carpus. 



6. Absence of supinator brevis. 



7. Insertion of caudo-femoralis into patella. 



8. Semi- and presemimembranosus fused almost to insertion. 



9. Marked expansions from hamstrings to calcaneum forming 

 a sheath for the tendo Achillis. 



10. Only an ischial origin for the biceps femoris. 



1 1 . Usual absence of bicipiti accessorius. 



12. Constant presence of straight and reflected heads to rectus 



femoris. 



13. Usual presence of femoral origin of tibialis anticus (Sub- 



ungulata the exception). 



14. Usual presence of femoral origin of extensor longus digitorum 



(Elephant the exception). 



15. Peroneus longus can be traced up to femur with external 



lateral ligament. 



19* 



