1866.] ON THE ANATOMY OF THE CRESTED AGOUTI. -107 



sacral vertebra. It is inserted by one large tendon into the summit 

 of the peroneal trochanter, and by several smaller ones (slight fasciae 

 intervening) into the outer and posterior surface of the same tro- 

 chanter (fig. 5, G. med.). 



It is precisely similar in the Guinea-pig, even to the several pecti- 

 nated-like tendons of insertion on the peroneal trochanter. In the 

 Rabbit and Hare it is very thin, but the insertion presents more of 

 a single flat tendon. 



We found the gluteus minimus to be a very small muscle arising 

 from the concave outer surface of the ilium, and having an insertion 

 by a single strong tendon into the extremity of the peroneal tro- 

 chanter (fig. 5, G.min.). This also answers to what is present in 

 the Guinea-pig. The Hare and Rabbit, however, differ, as in them 

 this muscle is largest, and in great measure covers the scansorius. 



Scansorius. This muscle is present in Dasyprocta cristata, and 

 is about the same size as the gluteus minimus, but is hidden by the 

 gluteus medius. It arises by muscular fibres from the whole inferior 

 (anterior) margin of the ilium, and is inserted by a very strong ten- 

 don, which passes down underneath the upper extremity of the 

 vastus externus into the anterior margin of the greater (peroneal) 

 trochanter (fig. 5, Sc). 



This muscle is relatively smaller in the Rabbit, Hare, and Guinea - 



pig- 



The pyriformis has origin from the ventral surface of the sacrum, 



and, passing out superficial to the sciatic nerve, is inserted within 



the peroneal trochanter towards its summit. The anterior border of 



the muscle is intimately connected with the posterior border of the 



gluteus minimus. 



In the Guinea-pig it is also connected with the scansorius. 



The obturator interims is applied to the inner surface of the obtu- 

 rator foramen or fascia thereon, and, turning outwards, its strong 

 tendon has an insertion into the trochanteric fossa immediately ex- 

 ternal to the quadratus femoris. 



The yemelli muscles adhere closely to each other. One arises a 

 little above the spine of the ischium ; the other takes origin between 

 that spine and the tuberosity of the ischium. They are inserted toge- 

 ther into the trochanteric fossa, along with the obturator interims. 



These muscles and the obturator internus Meckel* mentions as 

 existing ordinarily in Rodents. 



Quadratus femoris. This is but a very small muscle, with an 

 attachment between the tuberosity of the ischium and the acetabu- 

 lum ; its insertion is into the trochanteric fossa (fig. 5, Q.f.). 



The obturator externus is large and fleshy, occupying the front of 

 the pelvis as high as the upper margin of the obturator foramen ; it 

 proceeds into the trochanteric fossa. 



The above five muscles present no important difference as to 

 attachments in the other Rodents examined. 



The biceps, strictly speaking, consists of two parts, although ex- 

 ternally they are indistinguishable, and indeed they are for the most 

 * Op. cit. vol. vi. p. 364. 



