MUSCULAR SYSTEM. 



where the whole head is easily withdrawn within the strong 

 arched and capaceous carapace, these muscles are exposed 

 on the sides of the cranium (Fig. 75. A.) as in warm-blooded 

 animals. The orbicularis palpebrarum, (Fig. 75. A, a,) is 



here thin and feeble, and chiefly appropriated to the large 

 moveable lower eye-lid. The oblique muscles of the eye-ball 

 are also very small, while the recti and the suspensorius oculi, 

 (Fig. 75. B. a) are more distinct and strong. The mylo-hyoideus 

 (Fig. 75. A. by) and the latissimus colli (75. A. c,) here form 

 a large panniculus carnosus, covering the whole of the lower 

 part of the sides of the neck. The spinalis cervicis, (A. d,) 

 here forms numerous strong detached bands, which prin- 

 cipally support the head, and retract it, when alarmed, within 

 the cavity of the trunk. Behind this muscle lies the inser- 

 tion of the longus colli, (A. /,) which has a similar action on 

 the neck. Between these extends downwards the latissimus 

 dorsi, (A. e,) tapering to the humerus, before which is the 

 extended latissimus colli, and the imperfect diaphragm, (A.#,) 

 extending over the peritoneal covering of the lungs. The 



