1903.] THE MUSCLES OF THE UNGULATA. 289 



Rectus ventrcclis [R. abdominis). — This, as usual, rises from the 

 ventral aspect of the pubis near the symphysis and is continueil 

 forward to the fii'st lib. Ventral to the anterioi- two oi- three ribs 

 it lies deep to the supracostalis, and here its fleshy fibres usually 

 cease and it is continued to the first i-ib by a thin aponeurosis. 

 Many authors describe it as ending at the third, fourth, or fifth 

 ribs, but wherever we have been able to repeat their dissections 

 we have always been able to make out a delicate continuation of 

 the muscle to the first rib. The number of linete transversfe varies 

 from five to ten but eight or nine is tlie commonest number ; they 

 are, however, not well mai'ked, and Steel (XIX.) has pointed out 

 that in the Ass their number varies in individual specimens. 



Pyramidcdis. — We have never seen this muscle in Ungulates, 

 and our experience agrees with that of Lesbres (Y.) and Meckel 

 (VII.). Mivart and Murie (XXIV.) weie certain of its presence 

 in Hyrax, but in our specimen it was undoubtedly absent. 



All the preceding ventro-lateral muscles of the belly- wall are 

 supplied by the intercostal nerves. 



Quadratus lumborum, — This is a much narrower muscle in the 

 Ungulata than in Man, and is attached posteriorly, by a narrow 

 tendon, to the sacro-iliac joint or to a tubercle on the ilium close 

 by. Anteriorly it is inserted into the lumbar transverse processes, 

 and usually into the heads of several of the last ribs. In the 

 Hyrax (74) it goes to the posterior twelve ribs, in the Che^^?otain 

 (20) into five, in the Horse (64, 65), Pig (4), and Elephant (81) 

 into two, while in the Bovidse its costal insertion seldom extends 

 beyond the last rib. 



Psoas magnus. — This rises from the transverse processes of all 

 the lumbar vertebrte as well as from the sides of the bodies, it often 

 also rises from a few of the lower thoracic bodies ; its insertion is 

 as usual into the lesser trochanter. In the Hippo j)otamus (1) it 

 comes from the last two thoracic as well as the lumbar vertebrae. 

 In the Pig (9, 11) it is not well developed and only comes from 

 the lumbar region. In the Elephant (81) its attachment seems to 

 be the most extensive, as in that animal it rises as far forward as 

 the last four thoracic vertebi'se as well as the last four ribs near 

 their heads. 



The Psoas j^arvits was present in every animal of which we have 

 records except the Red River-Hog (11), and we have no doubt of 

 its being a very constant muscle in Ungulates ; it rises from the 

 bodies of the last three or four thoracic, and several of the lumbar 

 vertebrse ; it is inserted by a ribbon-like tendon into the ilio- 

 pectineal eminence. 



The Jliacus is a small muscle and is laterally compressed ; it 

 rises from the iliac fossa, the ventral sacro-iliac ligament, and the 

 margin of the sacrum. Before its insertion it blends with the 

 psoas. Murie, in the Giraffe (XXXII.), noticed that the iliac and 

 sacral origins remained separate for some time, and we found the 

 same in the Harnessed Antelope (55), though it certainly is not 

 always the case in Ungulates. 



Proc. Zool. Soc— 1903, Vol. II. ISo. XIX. 19 



