468 University of California Publications in Zoology [Vol. 13 



tuberosity {lat. dor., pi. 39). Its tendon joins that of the teres 

 major just before their common insertion. The latissimus dorsi is a 

 strong adductor and flexor of the foreleg, and is well developed in 

 the gopher where it helps to produce the downward and backward 

 stroke of the arm in digging. 



7. Sternomastoideus {stm., fig. 0). — This is primarily a muscle 

 of the head, but may be considered briefly here. It arises from the 

 manubrium of the sternum and the sterno-clavicular ligament, and 

 is inserted on the lateral and caudal surfaces of the mastoid 

 process of the skull. It draws the head downward and sidewise. 



8. Cleidomastoideus {dm., fig. 0). — This muscle in the gopher 

 is distinctly divided into two parts, as shown in the figure. Both 

 parts arise on the dorsal surface of the mastoid process of the 

 skull, the lateral part superficial to the mesial part. The inser- 

 tion is on the cephalic surface of the clavicle, the lateral part 

 occupying the outer third and the mesial part the inner two- 

 thirds. The cleidomastoideus acts both on the head and on the 

 shoulder girdle ; the head is drawn downward and sidewise when 

 the clavicle is fixed, and the shoulder is drawn forward and 

 upward when the head is fixed. 



9. Basioclavicularis (hasio., fig. S) arises on the ventral border 

 of the transverse process of the atlas and passes laterad and caudad 

 beneath the sternomastoideus and cleidomastoideus to be inserted 

 on the anterior surface of the lateral fourth of the clavicle, and 

 the cleido-humeral ligament. In the rabbit this muscle arises on 

 the basioccipital and sphenoid bones of the skull. This muscle 

 probably acts in both directions, drawing the head to the side or the 

 shoulder forward, depending on which part is fixed. 



Fig. 0. Ventro-lateral view of muscles of the neck and shoulder of the 



gopher, X li 



acd. — acromiodeltoideus pec. ter. — pectoralis tertius 



tasio. — basioclavicularis seal. — scalenus 



J)ic. — biceps brachii ser. ant. a — serratus anterior, cervical 

 bra. — brachialis portion 



elm. — cleidomastoideus ser. ant. b — serratus anterior, thoracic 

 cor. br. — coracobrachialis portion 



di. — digastric sth. — sternohyoideus 



mas. — masseter stm. — sternomastoideus 



omo. — omohyoideus tri. long. — triceps, caput longum 



pec. pri. — pectoralis primus tri. lat. — triceps, caput laterale 



pee. guar. — pectoralis quartus tri. med. — triceps, caput mediale 

 pec. see. — pectoralis secundus 



