1874.] MYOLOGY OF PHRYNOSOMA. 83 



and does not join any muscle of the leg, as it does in L. belli, where 

 this tendon, after joining that of the gastrocnemius, is inserted into 

 the back part of the head of the fibula. In that memoir * I was 

 induced to consider this muscle homologous with the pyriformis 

 by reason of its general aspect. It arises from the under surface of 

 the caudal vertebrae, a surface which is continuous with the under 

 surface of the sacrum t; its tendon passes out of the pelvis over a 

 pulley, as it were, formed by a ligament which goes from the posterior 

 end of the ilium to the outer and posterior angle of the ischium, and 

 which I have ventured to name the ilio-ischiatic ligament. Now this 

 ligament appears to occupy the position of the greater sacro-ischiatic 

 ligament in the human subject. These facts give this muscle quite the 

 facies of a pyriformis. Meckel was so struck with this resemblance 

 that he remarked that it " entspricht dem birnformigen Muskel des 

 Menschen " J. It corresponds to the muscle termed femoro-caudal § 

 by Mr. Miyart in the Iguana and Chamceleon ; the muscle termed 

 pyriformis in the former appears to be partly represented in my spe- 

 cimen by a muscle which I have termed coccygeus externus. As a 

 figure of the pyriformis was given in my memoir on L. belli, I did 

 not consider it necessary to repeat it. 



Coccygeus externus (figs. 4 & 5, C.E.) arises from the lower edge 

 of the outer extremity of the transverse processes of the first and 

 second caudal vertebrae, and is inserted into the ilio-ischiatic ligament 

 at a point corresponding to the origin of the semitendinous and 

 behind the quadratus femoris. 



Coccygeus inferior (fig. 4, C.I.) or internus (ischio-caudal in 

 Chameleon) resembles that muscle in L. belli in every thing except 

 that it arises only from the fifth and sixth caudal vertebras' instead 

 of from the tenth to the third. 



Iliacus arises from the lower surface of the symphysis ischii and 

 from the inner end of the same aspect of the pubis ; the fibres con- 

 verge and are inserted into the summit of the trochanter of the femur. 

 It resembles the same muscle in L. belli, and corresponds to the 

 second and third part of the pectineus as figured in Mr. Mivart's 

 paper on the Iguana. My reasons for considering this to be homo- 

 logous with the iliacus in anthropotomy are as follows :— In the first 

 place the insertions agree ; for it appears to me that there can be no 

 doubt that the trochanter of the femur in lizards is the tibial tro- 

 chanter, and therefore corresponds with the trochanter minor in 

 human anatomy. Secondly, although the fibres are not derived 

 from the right bone, they face as it were the right direction, viz 

 towards the ventral surface of the body. That the muscles termed 

 * Loe. cit. p. 173. 



t In the Tropidohpisma referred to above, I found that the anterior fibres 

 ot this muscle actually arise from the under surface of the second vertebra of 

 the sacrum. 



% Vergleichende Anatoruie, Thed iii. pp. 152, 153. 



§ The Eev. Prof. Haughton has described this muscle in the Crocodile under 

 the name in. extensor femoris caudalis, Ann. Nat. Hist. 1868 ; it is also men- 

 Socl867 G " nther in his memoir on the lizard Hatteria, in Trans. Roy. 



6* 



