1905.] ANATOMY OF THE LEATHERY TURTLE. 297 



muscular, and in front form a rounded tendon that runs forward 

 above the transverse process of the last cervical vertebra towards 

 the anterior cervical vei-tebrss. Its insertion was, unfortunately, 

 not seen. Posteriorly, this mass is attached partly to the second 

 rib, partly to the sides of the second dorso -lumbal- vertebra, and 

 partly goes on directly above the neck of the second and succeeding 

 ribs. Part a (interspinales) in this region foi'ms a definite 

 strand of muscle running between the spines of the last cervical 

 and first two dorso-lumbar vertebra?. 



These degenerate muscles could not be followed beyond the 

 sacrum, owing to injury of that part, but behind the ninth rib 

 they showed no signs of diminution, so that probably, as in very 

 young animals, they passed on over the sacrum. 



In Chelonia in general these muscles terminate from the second 

 to the eighth ribs in the adult, while the interspinales are entirely 

 lost. 



As regards these muscles, therefore, Dermochelys is less spe- 

 cialised than the rest of the Chelonia. And as the degeneration of 

 the back-muscles is due to the immobility of the carapace, we 

 may infei- that the relative softness of the carapace in Dermochelys 

 is a primitive condition — a stage in the development of a ti'ue 

 carapace, and not a secondarily acquired softness brought about 

 by retrograde modification of a hard carapace. 



Muscles of the Shoulder Girdle mul Fore Lwib. 



Collo-scapida7'is (text-figs. 55 &. 60. 40). — Origin : from the 

 lateral parts of vertebrae iii., iv., v., vi., vii. Insertion : upon 

 the median border of the scapular fossette and upon the median 

 surface of the head of the scapula. 



This muscle is separated by the roots of the brachial plexus 

 into four layers. The insertion does not agree mth that given by 

 Fiirbringer for Sphargis and C/felone. 



Another muscle (text-figs. 55 & 59. 40 «), which I cannot very 

 satisfactorily identify, may possibly be part of the collo-scapularis. 

 It takes origin from the lateral parts of the second vertebra in 

 forward continuation of the preceding muscle, and is inserted 

 upon the upper end of the scapula just dorsal to the insertion of 

 the posterior part of the sphincter colli. 



Testo-coracoideus (text-figs. 55, 57, 58, & 60. 42). — Origin : the 

 plastron, along a line that runs diagonally forward and outward 

 along the posterior edge of the outer part of the origin of the 

 pectoralis, and thence passes behind the arm to the carapace and 

 along the anterior border of the second rib to the hinder margin of 

 the scapular fosette. The origin from the plastron is fleshy, from 

 the border of the rib tendinous. 



Insertion : fleshy, to the deep surface of the posterior half of 

 the inner end of the coracoid, and by thin tendinous aponeurosis 

 along the coraco-clavicular ligament and down the inner border 

 of the scapula very nearly to its dorsal end. 



