680 MB. F. G. PARSONS ON THE [Nov. 20, 



the sole, lying beneath the head of the astragalus instead of pro- 

 jecting from the inner side of the foot as in the Tree-Porcupines. 

 There are three cuneiforms and a cuboid. 



The two phalanges of the hallux are. distinct, as they are in 

 Hystrix and Erethizon ; in Sphingurus they are fused together. 



The Muscular System. 



The muscles of Atlierura were found to resemble very closely 

 those of Hystrix, described in the "Myology of the Sciuromorphine 

 and Hystricomorphine Rodents." l In that paper I stated that I 

 had only noticed two definite muscular characteristics of the 

 Hystricidae as a family : — 



1. The latissimus dorsi at its insertion wraps round the lower 

 border of the teres major. 



2. The scalenus anticus is absent. 



Both of these points are noticeable in Atlierura. 



The points of difference suggested between the Tree- and the 

 Ground-Porcupines were much more numerous, and I have care- 

 fully tested them on Atlierura : — 



1. The digastric agrees with Hystrix in only having a slight 

 constriction between the two bellies, in this constriction a thin 

 layer of tendinous fibres is found on the surface. It differs from 

 Sphingurus in not having a strong tendinous slip from the posterior 

 belly to the hyoid bone. 



2. The omo-hyoid is absent, agreeing with Hystriv, in which it 

 is either absent or rudimentary, and differing from the Tree- 

 Porcupines, in which it is a large muscle. 



3. The levator clavicular rises from the basioccipital bone as in 

 Hystrix. In the Tree-Porcupines it comes from the atlas. 



4. The sterno-scapularis rises from the first part of the bony 

 sternum, not the leaf-shaped cartilage. A few fibres go to the outer 

 part of the bony clavicle, the rest are continued as the claviculo- 

 scapularis, which runs to the spine of the scapula but only covers 

 the outer part of the supraspinatus. This arrangement corresponds 

 with that found in Hystrix, in which the two parts of the sterno- 

 scapularis are continuous, in Sphingurus they are practically 

 separate. 



5. The biceps cubiti has only the long head as in Hystrix. In 

 the Tree-Porcupines both heads are present. 



6. The coraco-brachialis is inserted from just below the insertion 

 of the latissimus dorsi to just above the internal condyle by one 

 continuous attachment. The musculo-cutaneous nerve passes 

 through the muscle, i. e. a few fibres which are inserted lowest 

 pass superficial to it. If we regard the musculo-cutaneous nerve 

 as the separation between the second and third heads of the 

 coraco-brachialis, both these heads are present in Atlierura, and 



1 P. Z. S. 1894, p. 251. 



