Proceedings of the Scientific Meetings of the Zoological Society of London 1866

Page 443

1866.] ON THE ANATOMY OF THE CRESTED AGOUTI. 407 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 tro­chanter (fig. 5, G. med.). It is precisely similar in the Guinea-pig, even to the several pecti­nated- 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. W e 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 tro­chanter (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 ten­don, 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- Thepyriformis 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 internus is applied to the inner surface of the obtu­rator foramen or fascia thereon, and, turning outwards, its strong tendon has an insertion into the trochanteric fossa immediately ex­ternal to the quadratus femoris. The gemelli 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 toge­ther into the trochanteric fossa, along with the obturator internus. 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 acetabu­lum ; its insertion is into the trochanteric fossa (fig. 5, Q.fl). 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 ex­ternally they are indistinguishable, and indeed they are for the most * Op. cit. vol. vi. p. 364.