JITOLOGY OF OPISTHOCOMUS CEISTATUS. 363 



part of the middle third. It is inserted into the base of the great trochanter, its external 

 surface, below the medius and above the origin of the vastus extemus. 



The gluteus quartus is a small muscle arising from the prominent process of bone 

 which springs from the posterior acetabular border. It is inserted into the great tro- 

 chanter of the femur, behind the medius and on the same plane. This muscle resembles 

 rather the gemellus superior than a fourth gluteus, especially as its position is imme- 

 diately above the obturator internus. 



There is a somewhat peculiar muscle, which I am inclined to think is the semimem- 

 branosus. It arises from the shelving process of the ischium, and from the surface of 

 bone below and behind it, by muscular fibres. It increases in size as it passes down- 

 wards and forwards, and is inserted into the lower end of the femui, behind the outer 

 head of the gastrocnemius and the bicipital loop. A few of its fibres extend as low 

 down as the posterior surface of the upper extremity of the tibia. The great sciatic 

 nerve lies superficial to it. 



The femoro-caudal muscle is connected by a small band of muscular fibres with the 

 preceding muscle. 



The obturators, adductors, and quadratus femoris are present and well developed, but 

 present no special peculiarities. 



The psoas, iliacus, and pectineus are rudimentary. 



The great sciatic nerve is divided into peroneal and popliteal from its exit through 

 the ischiatic foramen. They lie parallel, and are enveloped in the same sheath. About 

 the middle of the thigh there is an intercommunicating branch. In the common 

 Pigeon &c. this division only takes place, as in Man, opposite the lower third of the 

 thigh. Probably it is accidental, or if not, is present occasionally in diflierent specimens 

 of the same species of birds. 



The external popliteal (peroneal) nerve passes through the bicipital loop with tendon 

 of biceps. This is constant in birds. 



The peronceus longus is a broad and expanded muscle at its origin. It arises by an 

 aponeurosis from the mesial tubercle of the tibia, which conceals the upper half of the 

 tibialis anticus muscle. It springs also by fleshy fibres from the whole length of the 

 rudimentary fibula, and it receives a few additional fibres from the tibia. The tendon 

 resulting from its fieshy belly divides opposite the lower third of the tibia into two 

 portions, an anterior and a posterior. The anterior tendon terminates on the dorsal 

 aspect of the foot in a broad expansion, which is inserted into the base of the first 

 phalanx of the external digit. The posterior tendon follows the usual course. 



The peroneal nerve has the same relation to this muscle as in the higher animals. 



The peronceus hrevis arises from the remainder true portion of the fibula, also from 

 the lower two thirds of the shaft of the tibia. It is inserted by a short tendon into the 

 base of the outer metatarsal bone. 



J-'he tibialis anticus (PI. LXV.) is a large fleshy muscle. Its origin is average. It is 



3c2 



