18G6".] ON THE ANATOMY OF THE CRESTED AGOUTI. 395 



The internal oblique and transversulis are so closely adherent as 

 to seem but one. They have the usual attachments of the internal 

 oblique, their only peculiarity being their relation with regard to the 

 rectus muscle. In the Hare there is also a close relation between 

 these two muscles, but in some parts the fibres are much more easily 

 separated fiom each other. 



Rectus abdominis. This muscle is nearly inseparable from the 

 external oblique over the cartilages of the ribs, and is also conjoined 

 to the serratus magnus at its anterior part. Its fibres, moreover, can 

 be traced onwards as far as the first rib. It is distinct and well de- 

 fined from the ensiform cartilage to about the umbilicus ; but from 

 this last point to the symphysis it is closely united with the internal 

 oblique and transversalis, with fibres, however, which are clearly 

 longitudinal. 



At the pelvic attachment the muscles of the right and left sides 

 cross each other precisely in the manner so well described by Prof. 

 Owen* as occurring in Capromys fournieri, and afterwards by C. L. 

 Martin in Myopotamus coypusf and Octodon ctnningii^.. 



The belly of the psoas parvus is small in volume, but it has a long 

 tendon of insertion. It arises by muscular fibres from the bodies of 

 the antepenultimate and penultimate lumbar vertebrae ; its narrow, 

 strong tendon expands just as it is inserted into the brim of the 

 pelvis. 



It is nearly alike in the Hare and Guinea-pig. 



The psoas magnus, on the contrary, is exceedingly large, and is 

 more or less separated behind (below) into distinct fleshy fasciculi, 

 especially where the anterior crural nerve pierces it. It arises from 

 the vertebral surfaces of the bodies of the whole of the lumbar ver- 

 tebrae, and is inserted as usual. 



This muscle has the same apparent division in the Guinea-pig ; 

 but the fleshy fasciculi are not so distinct in the Hare. 



The iliacus takes origin from the inferior surface of the blade of 

 the ilium, and, joining the psoas, has its ordinary insertion (figs. 4 & 5, 

 II.). It is very thick and fleshy. It possesses the same characters 

 in the Guinea-pig ; but in the Hare it is very intimately united with 

 the psoas magnus. 



Quadratics lumborum. This is a remarkably elongated muscle, 

 extending beneath the bodies of the vertebrae as far forwards as the 

 eighth dorsal one. It gradually broadens backwards until its fibres 

 reach the transverse process of the last lumbar vertebrae, whence it 

 narrows, and, running upon the ventral surface of the sacrum, is in- 

 serted by a single tendon into its outer margin, namely on the 

 surface of the sacro-iliac synchondrosis, a strong tendon extending 

 to the posterior end of that surface. 



In the Hare, beautifully distinct tendons are sent to the ventral 

 surfaces of each of the transverse processes of the lumbar vertebrae ; 

 they are present also in the Guinea-pig. but not so well defined, by 

 reason of the colour of the flesh and diffused fat. 



* P. Z. S. 1832, p. 68. t P. Z. S. 1835, p. 173. 



\ P. Z. 8. 1836, p. 70. 



