Mackintosh — Muscular Anatomy of Cholcepus didactylus. 69 



is from sternum, first rib, and clayicle. Unfortunately this muscle was 

 destroyed in Professor Humphry's specimen, so that we were unable 

 to determine whether the above peculiarity was an individual or a 

 generic one. There was no trace of the slip from the cleidomastoid to 

 the trapezius in either Bradypus or Arctopitheeus. 



Omohyoideus was absent, and trachelo-acromialis (omo-atlanticus of 

 Professor Haughton), though it shares the same fate in Bradypus and 

 Arctopitheeus, is represented in Cholcepus by a very slender band of 

 muscle arising from the paramastoid process, and inserted, not into the 

 acromion process of the scapula, but into the fascia over the supra- 

 spinatus muscle in front of the insertion of the occipital rhomboid. 



Sternohyoideus and sternothyroideus were separate from one 

 another (as in Bradypus, but not as in Arctopitheeus), the former aris- 

 ing from the presternum and first rib, the latter from the presternum 

 alone, underneath the sternohyoid, which ia inserted into the ten- 

 dinous inscription of the digastric fusing with its anterior portion ; 

 the sternothyroid is inserted as usual into the side of the thyroid car- 

 tilage. 



Digastricus, which, as in Arctopitheeus, only merits its name from 

 the tendinous inscription placed opposite the angle of the mandible, 

 arises from the stylohyal bone (tympanohyal in Arctopitheeus), and ia 

 inserted into the lower jaw as usual. 



Mylohyoideus extends along the whole length of the mandible. 

 Geniobyoideus is normal. 



Hyoglossus runs from the ceratohyal and thyrohyal to the tongue, 

 and styloglossus to the same organ from the former of those two bones. 

 The muscles in connexion with the Fore limb were arranged as 

 follows: — 



Trapezius was with difficulty separable into superior and inferior 

 portions; .the former, which included the clavicular segment as well, 

 arose from the middle line of the neck and from the occiput, and was 

 inserted into the lower border of the scapular spine as far down as the 

 origin of deltoid ; the inferior part extended from the four upper dorsal 

 spines to the spine of the scapula. 



Bhomboideus is divisible into three parts, (a) major, arising from 

 the two lower cervical and three upper dorsal vertebrae, inserted into 

 the whole vertebral edge of the scapula, and completely covering the 

 small thin (b) minor, which extends from the sixth and seventh cervi- 

 cal vertebrse to the scapula opposite to the spine ; (c) occipital, quite 

 separate from the other two, arising, as its name imports, from the 

 occiput and inserted into the superior angle of the shoulder blade.* 



Teres major is a large muscle which arises, as usual, from the sca- 

 pula, and has the normal humeral insertion separate from, but close to 

 the attachment of latissimus dorsi, which has an extensive origin from 

 the spines of the third, fourth, fifth, sixth, and seventh dorsal vertebraa, 



This portion was absent in Arctopitheeus and Bradypus. 



