BY W. J. S. McKAY. 



269 



bone just anterior to the origin of the trapezius. Running out- 

 wards and backwards a muscular band develops, and this courses 

 over the side of the head and neck, to be presently joined by the 

 ventral division which arises from the malar, squamosal and 

 posterior mandibular regions. The conjoined muscles are prolonged 

 on to the dorsal aspect of the forearm, and there inserted on the 

 distal third of the external border of the ulna ; being thus related 

 to the dermo-flexor antebrachii, which is placed superficial and 

 distal to it. 



Ornithorhynohus. 



The panniculus has a similar arrangement, on the whole, in this 

 animal to the muscle in Echidna ; a few points call for notice. 



The muscle is well de\eloped, but is not by any means so thick 

 as in the Echidna, and though closely connected with the integu- 

 ment, there is little difficulty in dissecting it off. 



As we follow the ventral sheet forward the fibres have an 

 inclination towards the mid-line ; but there is no marked differen- 

 tiation into divisions as described in Echidna. A dermo-flexor 

 antebrachii is present attached to the distal extremity of the 

 ulna. When the superficial layer is raised, in the region of the 

 axilla, it is found that a deeper layer is differentiated off, and that 

 as it approaches the humerus this layer pierces the deep fascia, 

 and cleavage occurs in a plane parallel to its surface, a superficial, 

 middle and deep layers being the lesult. (Fig. 5, Pn. S., Fn. D. i., 

 Pn. D. ii.) The superficial layer (of the deep stratum), lying 

 above the tendon of the P. major, is inserted on the middle 

 third of the outer border of the pectooo-deltoid ridge ; and also, 

 as Smith (17) has pointed out, on to the outer part of the tendinous 

 intersection of the P. major (see post). The middle (Fig. 6, Pn. 

 D. iii.) division, hidden by the superficial, runs inwards and is 

 inserted on to the tendon of the P. major; being intimately con- 

 nected with the terminal fibres of the P. quartus. The deep 

 division (Fig. 6, Pn. D. ii.) runs inwards, and approaching the 

 outer border of the P. major forms an inverted A with that muscle, 

 a tendinous intersection intervening between the muscular fibres 

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