74 MR. A. SANDERS ON THE [Jan. 6, 



Sterno-mastoid (figs. 1 &3, S.M.) arises from the anterior end of 

 the articular surface between the sternum and the clavicle, and from 

 the extremity of the cross piece of the interclavicle ; it passes forward 

 and dorsad to be inserted into the posterior surface of the cranium, 

 between the origins of the digastric and the complexus. 



Neuro-mandibularis (fig. 3, N.) in this species runs obliquely 

 downward and forward, instead of directly downward as in L. belli 

 and P. japonicum. It arises from the outer edge of the complexus, as in 

 those lizards, and from the fascia of the back at the level of the scapula, 

 and is inserted into the posterior point of the mandible. This 

 muscle does not appear to be represented in Iguana*. 



Ectopterygoid is very small, and only corresponds to the internal 

 part of the same muscle in L. belli and P. japonicum ; it is covered 

 by the muscles of the hyoid arch, and arises from the external edge 

 of the pterygoid, and is inserted into the inner surface of the angle of 

 the mandible. 



Temporalis is a much less extensive muscle than "in either P. 

 japonicum or L. belli. It is triangular, and arises from what appears 

 to be the squamosal and postfrontal, anterior to the quadrate; it is 

 inserted into the upper surface of the mandible, in front of the arti- 

 culation of that bone with the quadrate. 



Entopterygoid (fig. 3, En. P.) is the principal muscle for moving 

 the lower jaw. It arises from the posterior apophysis of the parietal, 

 from the squamosal, and also from the anterior side of the quadrate, 

 and is inserted into the upper edge of the mandible for about one 

 third of its length, in front of the articulation with the quadrate. 

 A muscle which I interpret as being homologous with the tensor 

 tympani does not appear to be present in Iguana ; it arises from' the 

 columella, and from the anterior and upper point of the prootic, 

 covered by both pterygoids, and is inserted into the pterygoid bone ; 

 it was found in both P.japonicus and L. belli as well as in the present 

 subject. 



Digastric (fig. 3, Di.) arises from the point where the squamosal 

 and exoccipital meet, and descends to be inserted into the posterior 

 end of the mandible immediately above the insertion of the neuro- 

 mandibularis. This appears to represent the posterior part of the 

 digastric of the human subject. 



The dorsal muscles appear to follow the usual arrangement. The 

 sacro-lumbalis commences in the tail, and is partly inserted into the 

 ilium, from which bone it takes a fresh origin. The longissimus dorsi 

 is not distinguishable from the spinalis dorsi ; they both commence 

 in the caudal region. The complexus resembles that of L. belli ; 

 neither a trachelo-mastoid nor a transversalis colli could be found. 

 A small muscle arises from the transverse process of the axis above 

 the insertion' of the levator scapulae, and is inserted into the basi- 

 occipital ; this differs from the rectus posticus of L. belli, and perhaps 

 represents a rectus lateralis. 



Rectus anticus major resembles the same muscle in L. belli, but 

 in addition arises from the four cervical and three anterior dorsal ribs. 



* P. Z. S. 1867, p. 766. 



