392 Haeris Hawthorne Wilder, 



outer surface. Ä semi-detached slip, apparently belonging to the 

 procoracohumeralis, lies in the form of a narrow ribbon along its 

 dorsal border, at first between it and the lateral slip of the super- 

 ficial rectus and then between it and the dorsal portion of the 

 supracoracoideus. Its origin is beneath the rest and nearer the 

 glenoid fossa; its insertion appears quite separate and associated 

 rather with the accessory portion of the dorsalis scapulae than with 

 the procoracohurneral. 



M. rectus superficialis hypobranchialis posterior 

 (rhp). Three more or less separate elements belonging to this System 

 of trunk mnscles become differentiated from the general mass and 

 are inserted upon the external surface of the Shoulder girdle. They 

 consist primarily of a medial and a lateral portion, which em- 

 brace the procoracoid between them as they pass to their insertion,. 

 but the lateral slip is again capable of division into two because 

 of a double origin. The details of these slips are as follows: 



a) medial slip. This slip arises in the form of a thin sheet 

 from the third myocomma, the origin including the lateral half of 

 the distance between the procoracoid cartilage and the mid-ventral 

 line. From this origin the fibers converge to a narrow insertion 

 upon the external surface of the Shoulder girdle, just anterior to 

 the glenoid fossa, and thus on neutral ground between the Shoulder 

 pieces although at the base of the procoracoid. 



b) lateral slip. This portion is double at its origin and con- 

 sists of two heads, medial and lateral, although both soon unite and 

 pass around the lateral side of the procoracoid as a Single slip. The 

 medial head arises from the third myocomma as a continuation 

 laterally of the medial lateral slip (a), but passing laterally soon 

 joins the lateral slip (b). Thus this head and the entire slip (a) 

 represent a continuous superficial sheet that arises from myo- 

 comma 3 and is parted into two unequal portions by the procora- 

 coid cartilage. The lateral heacl is much the larger, and arises 

 from the posterior aspect of the first ceratobranchial cartilage and 

 runs posteriorly, picking up on the way the small medial head. 

 The combined bündle passes around the lateral margin of the pro- 

 coracoid, and inserts upon the dorsal margin of this cartilage, in 

 the region of and including the slightly projecting angle found there. 

 The lateral head, which arises from the hyobranchial skeleton, is called 

 by DßÜNER, M. procoracohyoideus (better M. hyoprocoraccideus) ; the 

 medial head is plainly a semi-detached portion of the medial slip (a). 



