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Show 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. N o w 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 " %. It corresponds to the muscle termed femoro-caudal § by M r . Mivart in the Iguana and Chamaleon; the muscle termed pyriformis in the former appears to be partly represented in m y specimen by a muscle which I have termed coccygeus externus. As a figure of the pyriformis was given in m y 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 semitendinosus and behind the quadratus femoris. Coccygeus inferior (fig. 4, C.I.) or internus (ischio-caudal in , Chamceleon) resembles that muscle in L. belli in every thing except that it arises only from the fifth and sixth caudal vertebrae 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 converge 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 M r . Mivart's paper on the Iguana. M y reasons for considering this to be homologous with the iliacus in anthropotomy are as follows :-In the first place the insertions agree ; for it appears to m e that there can be no doubt that the trochanter of the femur in lizards is the tibial trochanter, 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 * Loc. cit. p. 173. + In the Tropidolepisma referred to above, I found that the anterior fibres of this muscle actually arise from the under surface of the second vertebra of the sacrum. X Vergleichende Anatomie, Theil iii. pp. 152, 153. § The Rev. Prof. Haughton has described this muscle in the Crocodile, under the name m. extensor femoris caudalis, Ann. Nat. Hist. 1868; it is also mentioned by Dr. Giinther in his memoir on the lizard Hatte/ria, in Trans. Roy. Soc. 1867. 6* |
