178 Mil. i\ a. PAESdNS oir Hihb [Jan. l4. 



Muscles of Posterior Extremity. 



Gluteus Maximus, Tensor Faseiw Femoris, and Sariorius. — The 

 description already given ' applies perfectly to the Myomorpha ; the 

 tensor fasciae and sartorius are, however, as a rule less well marked, 

 and there is also a closer union between the posterior border of the 

 gluteus maximus and the anterior border of the biceps femoris. 

 The bony insertion of the gluteus maximus is into the middle of 

 the femur except in Criceius, where it is also attached to the 

 external supra-condylar ridge of the femur, and in Rhizomys, 

 where it is attached almost entirely to the third trochanter in the 

 upper part of the bone. The sartorius and tensor fasciaa femoris 

 are best marked in Cricetus, while in Georydius they are practically 

 absent. 



Gluteus Medius and Minimus. — These muscles present no 

 differences from those already described in other Eodents. 



Scansorius. — The scansorius is so closely fused with the gluteus 

 minimus, that it is only possible to make it out as a distinct muscle 

 in Cricetmnys, though even there the separation is not very 

 clear. 



Pyriformis. — This muscle is also much more closely fused with 

 the gluteus minimus than in the other Eodents; indeed, the 

 Myomorpha are remarkable for the unsatisfactory differentiation 

 of the muscles composing the gluteal mass. 



Obturator Jnternus, Krternus, and Oemelli. — These muscles 

 correspond to their descriptions in the other Rodents. The 

 anterior gemellus is always better marked than the . posterior 

 one. 



Quadratus Femoris. — There is usually a very slight tendon at 

 the insertion, the muscle being triangular as in the Hystricomorpha 

 and differing from the quadrilateral Sciuromorpliine type; it is 

 always large and distinct. 



Biceps Femoris. — In Myoxus, Mus barharus, and Mus rattus the 

 two parts of which the biceps is composed are closely united and 

 have one continuous insertion, as is the case in the Hystricomor- 

 phine Eodents. In the other Myomorpha the two parts are easily 

 sepai'able, as they are in Sphingurus^ . When this happens, it is 

 the upper part which rises from the anterior caudal vertebroe and 

 is inserted into the outer side of the patella and ligamentum 

 patelte, while the lower part rises from the tuber ischii and is 

 inserted into the fascia on the outer side of the leg. In certain 

 cases, e. g. Cricetomys and Myodes, the upper portion is very closely 

 connected to the gluteus maximus ; while in Cricetus it is so 

 closely blended with that muscle, that it has already been described 

 as a part of the gluteus maximus which is inserted above the 

 external condyle of the femur. 



In Georychus, Bathyergus, Rliizomys, and Heteromys the two parts 

 are separate from one another and from the gluteal. 



> P.Z.S. 1894. p. 282. 

 = P.Z.S. 1894, p. 284. 



