76 OUTLINES OF EQUINE ANATOMY. 



pying tlie inner half of tlie surface, extending from tlie 

 anterior margin to the posterior angle. The posterior 

 triangle, convex and rounded, extends on to the posterior 

 angle of the bone. The anterior triangle is continuous on. 

 its outer margin with a facet, on the anterior part of the 

 outer surface for os unciforme. Internally it is con- 

 tinuous with the inner articulatory part of this surface, 

 which is triangular, occupying the inner angle of the 

 surface, separated postero-externally from the other part 

 by a perforated concavity. It is slightly continued on to- 

 the inner surface of the bone for articulation with trape- 

 zoides. "With this part os scaphoides comes in contact, while 

 OS lunare occupies the outer part. The inferior surface is 

 flattened, slightly convex anteriorly, slightly concave pos- 

 teriorly, and has four margins. The anterior margin is. 

 convex, extending farthest backward on the inner side. 

 The posterior is not half the length of this, and is perfectly 

 straight. The outer margin is straight, but centrally pre- 

 sents a deep depression, roughened, and extending towards 

 the centre of the surface. Along the inner margin, at its 

 anterior part, is a small facet for articulation with the 

 inner small metacarpal bone ; this is continuous with the 

 main surface for os metacarpi magnum, and is continued on 

 to the inner surface, forming a small facet for the trape- 

 zoid. The inner surface presents three facets for trape- 

 zoides — one antero-superiorly elongated, one antero-infe- 

 riorly, shorter but deeper, and one posteriorly extending^ 

 from the posterior part of the inner concavity of the 

 inferior surface ; this looks forwards. The rest of the 

 surface presents irregular roughened concavities and 

 convexities for attachment of interosseous ligaments. _ The 

 outer surface presents articulatory facets for union with os- 

 unciform, between which the bone is rough for attach- 

 ment of interosseous ligaments. The anterior surface or 

 base forms an irregular parallelogram extended from side 

 to side, which centrally presents a roughened prominence 

 for attachment of the annular ligaments, superiorly and 

 inferiorly a groove bounded by the articular facets of the 

 upper and lower surfaces, 



OS UNCIFORME.— The outer bone of the lower row 

 articulates with cuneiforme, lunare, magnum, metacarpi 

 magnum, et parvum externum. It presents four surfaces,, 

 and a posterior very prominent angle. The su])ero- external 



