1916] HalUger: Anatomical Adaptations in the Pocket Gopher 465 



tuberosity. Besides affording motion to the skin of the trunk, the 

 eutaneus maximus in the gopher draws the leg backward and 

 assists in digging movements. The eutaneus maximus is a promi- 

 nent muscle in all the rodents examined, but it is especially well 

 developed in the rat, in which it forms a very heavy layer beneath 

 the skin of the caudal three-fourths of the trunk. 



2. Trapezius {trap., fig. N) is composed of three parts in the 

 gopher; in the rabbit there are only two parts. 



a. The cervical portion {trap, a, fig. P) arises from the mesial 

 third of the lambdoid ridge of the skull, from the entire length of 

 the nuchal ligament, and from the spines of the first, second and 

 third thoracic vertebrae and the supraspinous ligament. The 

 fibers pass laterad to be inserted along the whole length of the 

 spine of the scapula and on the fascia of the acromio-clavicular 

 articulation. This muscle is a thin, triangular layer, the function 

 of which is to draw the scapula dorsad and to rotate its glenoid end 

 forward. The rotating action of this and other muscles is explained 

 by considering the scapula as pivoted on a horizontal axis through 

 its center. Observation shows that much of its movement consists 

 of rotation around such an axis. 



6. The middle portion {trap, h, fig. P) of the trapezius arises 

 from the spinous processes of the fifth and sixth thoracic vertebrae 

 and the supraspinous ligament, and passes laterad and cephalad to 

 be inserted with the thoracic portion. 



c. The thoracic portion {trap, c, fig. P) arises from the spinous 

 processes of the eleventh and twelfth thoracic and first lumbar 

 vertebrae and the supraspinous ligament. It forms a narrow band 

 of fibers which pass forward and, after being joined by the middle 

 portion, are inserted on the proximal angle of the spine of the 

 scapula. The action of parts & and c is to draw the scapula back- 

 ward, and to rotate its glenoid end forward. 



3. Rhomhoideus capitalis {rhom. cap., figs. P, S) lies immedi- 

 ately beneath 2a. This muscle in the gopher is unlike any muscle 

 found in the other rodent forms studied. It resembles most nearly 

 the occipitosc»pularis of the cat (Reighard and Jennings, 1901, 

 p. 118). C. H. Merriam (1895, p. 102) describes this muscle in the 

 gopher under the name of the rhomhoideus. The rhomboideus capi- 

 talis is a strong band of fibers which take origin along the lateral 

 half of the lambdoid ridge of the skull, where the external half of the 

 origin is overlapped by the origin of the cleidomastoid. It passes 



