184 DR. R. W. SHUFELDT ON [Apr. 1, 



cated, but believe with Hoffmann tliat the muscle can be very well 

 described in its entirety, such as has been done in the present 

 instance. 



83. Gracilis. — This is a strong and rather thick ribbon of muscle 

 that passes obliquely down the antero-inferior aspect of the thigh, 

 its lower margin being in contact with the sartorius for its entire 

 length. The (/racilis arises from that process, immediately anterior 

 to the acetabulum, which is crossed by the pubo-ischiadic suture, its 

 origin being tendinous. For the most part it is inserted into the 

 fascia covering the tibial side of the knee-joint, while a few of 

 its fibres join those of the sartorius, the two muscles being very 

 intimately miited, here, at their insertion. Sanders found a 

 gracilis as well as a sartori^is muscle in both Liolepis and Platy- 

 flactj/his ; but Hoffmann seems disinclined to recognize the existence 

 of the latter in Lizards (Bronn's ' Thier-Reichs,' Kept. 22-24 Lief. 

 1881, p. 645). They are both undoubtedly handsomely developed 

 here in Heloderma suspectum. 



84. Sartorius. — In this we have a great muscular sheath that 

 envelops nearly the entire ventral aspect of the thigh, and which 

 arises from the hamular process of the pubis, as well as from the 

 ilio-ischiadic ligament. Below, it is inserted into the proximal end 

 of the tibia, upon its anterior aspect, just below the head of the 

 bone. 



85. Pelvo-tibialis. — There is a small muscle in this region that 

 lies immediately beneath the (/racilis for nearly its entire length, and 

 which I will here describe under the name given it by Sanders. 

 Prior to that writer, Mivart had designated it in the Iguana as the 

 " tibial adductor,"' and subsequently Hoffmann termed it the 

 " M. puho-ischio-tihialis lateralis."' Of these several names I con- 

 sider the one bestowed upon it by Sanders to be decidedly the 

 best one. In Heloderma it arises by a single tendinous head from 

 the ischium just in front of the acetabulum. Passing down the 

 antero-ventral aspect of the thigh as a narrowish ribbon of muscle, 

 it again becomes tendinous as it nears the tibia, enters the popliteal 

 space, and is inserted, just below its head, upon the mesial aspect 

 of the bone just mentioned. 



8(). Semimev/branosus. — What I describe here as the ilio-ischiadic 

 ligament is a tendinous ligamentous arch which arises from the tu- 

 berosity of the ischium, and passing round the inside of the thigh to 

 the front is there inserted into the ilium. From this arch our rather 

 slender semimenibranosus arises and jiasses down to be inserted into 

 the outer side of the proximal end of the tibia. I can find no origin 

 for it upon the ischium in Heloderma. 



8". Seinitendinosus. — This muscle is handsomely developed in 

 our present subject. It arises, tendinous, from the ilio-ischiadic 

 ligament, posterior to the line of the shaft of the femur. Becoming 

 carneous it forms a fusiform muscle which is concaved towards the 

 thigh and convexed upon its opposite aspect. Opposite the femoral 

 condyles its tendon appears, and this is bifurcated, one branch going 

 to the inner side of the proximal end of the tibia for insertion, the 



