1881.] On the Tendinous Intersection of the Digastric. 31 



posterior margin, the tendinous raphe, above described, is concave, 

 quite free from the hyoid bone, but attached to a fascial aponeurosis, 

 which passes backwards over it and the sterno-hyoid muscles. 



On removing this muscular expansion, the mylo-hyoid muscles are 

 found beneath, very thin, not extending half the distance between 

 the hyoid bone and the symphysis menti. 



In Tupaia ellioti the anterior bellies of the digastric also unite in the 

 middle line between the jaws, but there is no separate superficial 

 external lamina in direct continuation with the posterior belly as in 

 Gymnura rafflesii. The intersecting tendon is narrower but more dis- 

 tinct, arises as in that species from the upper margin of the muscle, 

 and is continued downwards, forwards, and inwards to unite with the 

 corresponding tendon from the opposite side across the mylo-hyoid, 

 precisely as in G. rafflesii ; but, unlike its condition in that species, 

 it is closely adherent to the muscle on which it lies, and is connected 

 by a strong fibrous aponeurosis with the body of the hyoid bone, while 

 the greater cornu receives also some tendinous fibres from the lower 

 margin of the posterior belly. The united anterior bellies pass forwards, 

 taking their origin from the tendinous raphe, and, separating slightly 

 near the symphysis, are inserted into the rami of the mandible, and 

 by a fibrous aponeurosis into the symphyseal angle. The mylo-hyoid 

 muscles, nearly wholly concealed by them, are, as in G. rafflesii, feebly 

 developed, and do not extend more than half their length. 



In Chiromys madagascariensis, the anterior bellies of the digastric 

 muscles are united between the jaws,* but in other Lemuroids, as also 

 in man, they are separate, each consisting of " two thick fleshy 

 bellies with a long and strong median tendon. "f In Loris gracilis I 

 found a strongly marked oblique tendinous intersection (which has 

 been described as a rudimentary tendon), J connected by a fibrous 

 aponeurosis with the greater cornu of the hyoid bone and also with 

 the surface of the mylo-hyoid in front of it, so that here we have 

 evidently a case of oblique tendinous intersection passing into 

 tendon. 



In E. macroceplialus and in E. minor, among the Chiroptera, I found 

 the anterior bellies double, the deep lamina united and forming a 

 horizontal muscular expansion extending backwards even behind the 

 hyoid bone, but wholly unconnected' with it, its posterior margin 

 being connected laterally with the tendinous intersection and 

 medially with a fascial aponeurosis loosely covering the sterno-hyoid 

 muscles. It is especially interesting to note that here, where union of 

 the muscles extends so far backwards, the tendinous intersection is 

 vertical, or nearly so, and the direction of the fibres of the deep or 



* Owen, " Trans. Zool. Soc," v, p. 43. 



f Murie and Mivart, " Trans. Zool. Soc," vii, p. 18. 



X By Van der Kolk and Yrolik, referred to by Murie and Mivart, loc. eit. 



