340 SHOULDER-GIRDLE IN MONOTREMES, 



Orxithokhyxchus. 



Owen does not mention these umsclt^s. 



CouES describes these muscles separately, as costo-scapularis, 

 serratus magnus s. anticiis, and levatores anguli scapulae. 



The costo-scapularis is described by Coues as arising from the 

 first three ribs. 



Leche does not mention these muscles. 



Meckel — " Serratus anticns in musculos duos, omnino separates, 

 secessit. Horum superior, fere quadratus, sex fasciculis vertebris 

 colli inferioribus quinque et dorsi primse inserltur, a margine 

 scapulse postico ortum ducens." 



"Inferior, multo longior, sed angustior, triangularis ab apice 

 scapulte inferiors fasciculis tribus ad costas tres proficiscens, 

 versus extremum anterius faciei earum externse inseritur." 



Cuvier and Laurillard, on PI. 266, figure these muscles in 

 fig 1, "f,?" grand dentele (scapulo-costien). The letter {g) close to 

 the letter o (teres major) is the costal part of the muscle, but the 

 other g appears to us to be really on the deep part of the acromio- 

 trachelien, as also shown in fig. 2. 



M. sterno-mastoideus et M. episterno cleido-mastoideus. 



Echidna : M. sterno-maxtoideiif, all authors. 



Orxithorhynchus : Sterno-mastoid, Owen ; Nutatcr capitis, Meckel ; 

 St erno -mastoid et Cleido- mastoid (?), Coues ; Cleido-mastoidien, et Stervo- 

 maatoidien ou trachelien, Cuvier and Laurillard. 



M. sterno-mastoideus. (Fig. 1, S.M.) 

 Echidna. 

 Origin. When the superficial layer of the panniculus and 

 the fascia beneath are reflected from the sternal region, the sterno- 

 mastoid is displayed. The muscle, closely connected with its 

 fellow of the opposite side, has an origin from the mid-line of the 

 mesosternum, as far back as the ventral extremity of the fourth 

 rib, and extending forward over the presternum and posterior half 

 of the median portion of the interclavicle. 



