262 ZAGLOSSUS. 



finally forms a great layer of adipose tissue that extends from the axilla to the 

 groin, next the body muscles. 



(5) A very remarkable muscle, named by Fewkes the dermo-flexor ante- 

 brachii, arises by a series of digitations from the eighth to the thirteenth ribs 

 (Plate 1, fig. 1, Id). The first of these is in contact with one of the sUps of the 

 dermo-dorsi cervicalis, at its ventral border. The entire muscle is somewhat 

 fan-shaped and its fibers converge and pass to a tendinous insertion into the 

 fascia investing the fore arm, about halfway on its ventral surface. Mivart 

 (1866) considers this muscle a posterior portion of the latissimus dorsi, but as 

 stated by Fewkes, its insertion is different, though its origin is similar. Mivart's 

 supposition, however, has much to recommend it. From a lateral view it is 

 seen that the origins of latissimus dorsi, dermo-dorsi cervicalis, and dermo-flexor 

 antebrachii form a practically continuous series of digitations from the ribs, as 

 is usual for the lalissimus. What may once have been thus a single muscle, 

 originating by digitations from the first to thirteenth ribs and inserting on 

 the ulna, may quite conceivably have become broken into three sections, as 

 here, the two posterior of which have become superficial in their attachments. 

 The function of the middle portion {dermo-dorsi cervicalis) has thus become 

 changed to that of a retractor of the bases of the dorsal spines, while the function 

 of the posterior part {dermo-flexor antebrachii) is still practically that of the 

 true latissimus, serving to approximate the fore arm while at the same time 

 drawing it posteriorly. Owing to the great anteroposterior extent of the arm, 

 the efficiency of the true latissimus is greatly lessened so that the transference 

 of the insertion of this posterior portion from the ulna to near the carpal region 

 results in a great gain of power for a burrowing animal. 



(6) What are evidently the dermo-extensores brachiales intimus, inferior, 

 et superior of Fewkes, are also present in Zaglossus as a narrow band of super- 

 imposed sheets about 10 mm. wide and 100 mm. long, from near the midline 

 of the panniculus at the back of the neck, passing to the fasciated sheath that 

 encircles the wrist and inserts on the ulna. 



(7) A muscle named by Fewkes the dermo-flexor cruris (Plate 1, fig. 1, dfc) 

 arises by a thin tendinous sheet from the spines of the coccygeal vertebrae, and 

 is joined by a few fibers of the overlying part of the general panniculus. The 

 broad sheet of muscle thus formed passes laterally and invests the lower hind 

 limb where on the external aspect it becomes a thin sheath of aponeurosis and 

 internally is muscular. From the distal part of this sheath a conspicuous 

 muscle band is separated and passes to a tendinous insertion 7 mm. long on the 



