36 FIELD MUSEUM OF NATURAL HISTORY ZOOLOGY, VOL. XIV. 



marsupial bone and proceeds to the mid-ventral line and the testes. It 

 is a well developed strand of muscle about one mm. in width but simply 

 parallels or covers but does not enclose the spermatic cord until near the 

 base of the testes where it nearly or quite surrounds the cord before 

 spreading over the base of the testes and becoming aponeurotic. 



MUSCLES OF THE SACRUM. 

 Plates III, V. 



Glutens maximus. Origin from the crest and the anterior part of the 

 acetabular border of the ilium and from the articular processes of the 

 sacral and anterior caudal vertebrae as well as from the tendinous fascia 

 covering the erector spinae as far caudad as the origin of the femoro- 

 coccygeus. Insertion somewhat divided, an anterior part on the cranio- 

 lateral and a posterior one on the caudo-lateral surface of the distal end 

 of the great trochanter of the femur. It is a broad fan-shaped muscle, 

 relatively thicker than in Didelphis, being fleshy from the erector 

 spinae. Its cranial border is thickened and somewhat curled around the 

 anterior fifth of the ilium and distad lies in the groove between the 

 glutens medius and the iliacus, continuing ectad of the proximal end of 

 the vastus externus to the cranial border of the biceps femoris to which it 

 has a short semitendinous attachment distad and ectad of its insertion 

 on the great trochanter. Its caudal border parallels the femorococcygeus 

 but except in the dorsal fascia is distinct from it. No separate tensor 

 fascia femoris is evident and it is doubtless fused with the glutens as in 

 various other marsupials. 



Glutens medius. Origin extensive from the dorsal fascia, the 

 laminar tendons of the caudal muscles, the transverse processes of the 

 sacral vertebrae, and the crest and ischial border of the ilium. Insertion 

 on the caudo-lateral proximal part of the great trochanter of the femur 

 ectad of that of the gluteus minimus which is distinct. It lies entad of 

 the gluteus maximus and is almost equal to it in superficial extent. It 

 is imperfectly divisible into two layers, the posterior one overlapping the 

 anterior. A similar bilaminar arrangement is reported in Phascolarctos , 

 Thylacinus, and Dasyurus, but not in Didelphis l and Cuscus (see Leche, 

 Bronn's Thierr., p. 853). It is likewise in Notoryctes (Thompson and 

 Hillier, 1905, p. 310). On its ental side it is somewhat connected with 

 the pyriformis not only near the insertion but also elsewhere except 

 along the anterior tendinous border of the pyriformis. Anteriorly it is 

 curled under from the crest of the ilium to the femur but in the distal 

 half of this extent its edge is free and merely overlies the gluteus minimus. 



1 Sidebotham (1885, p. 13) reports three layers in Chironectes. 



