Yol. 69.] SKELETON OF 0HXITH0DES3IU3 LATIDEXS. 389> 



the proximal articulation. All the surfaces of the carpals are- 

 very complex. The preaxial border of the proximal carpal is pro- 

 duced outwards into an elongated process of bone, truncated at 

 its extremity. This has on its proximal surface a spherical knob 

 of bone (PI. XXXIX, fig. 8, A), which articulates in the circular 

 pit on the distal articulation of the ulna (PI. XXXIX, fig. 7, A)*. 

 The dorsal surface of this process is concave, and here occurs a. 

 subcircular pneumatic foramen. This surface articulates apparently 

 with the lateral carpal. From this preaxial process on the ventral 

 side the bone narrows, first showing a convexity followed by a. 

 concavity, afterwards enlarging considerably in a proximal and 

 postaxial direction to the border. This expansion (PI. XXXIX,, 

 fig. 8, G) articulates with the convex condyle of the distal end and 

 the circular facet on the ventral surface of the ulna (PI. XXX'IX, 

 fig. 7, G, & fig. 6, fa.), and in a proximal and distal direction is 

 produced for the length of the distal carpal, articulating with it 

 on its inner face. The dorsal preaxial border is remarkably raised 

 proximally into a strong buttress, which juts out as a wedge- 

 shaped piece of bone, anchylosed to the carpal. The butt-end of 

 this wedge has a concave groove, in which the radius articulates. 

 (PI. XXXIX, fig. S, D). From this buttress to the postaxial. 

 border the bone narrows, and the surface is mainly convex, without 

 any peculiar feature. A process similar to that on the proximal 

 carpal occurs on the preaxial border of the distal, directed also 

 preaxially, and possessing, on its proximal surface, a facet for 

 articulation apparently with the distal end of the lateral carpal. 

 On its preaxial dorsal half, for the same distance as the buttress 

 for the radius on the proximal carpal, the bone is produced out- 

 wards and distally in such a manner that the two form a deep 

 quadrangular cavity. Whether a sesamoid bone occupied this 

 hollow it is not possible to say ; however, it is suggestive, for such 

 have been found near this point in the German specimens. The 

 postaxial half of the dorsal surface is nearly flat. The bone 

 gradually expands from the preaxial to the postaxial border, which 

 is produced distally outwards. The postaxial border is the apex 

 of an angle, formed by the conjunction of the ventral and distal 

 articulatory surfaces, which gradually converge together to this 

 point. The articulation for the radius on the proximal carpal is 

 an elongated groove, parallel to, and near, the dorsal surface, and 1 

 midway between the pre-postaxial borders (PI. XXXIX, fig. 8, 1)). 

 That for the ulna is much more complex (PI. XXXIX, fig. 8, 

 A, B, C). It consists preaxially of a hemispherical knob (A). 

 dorsal to which is a small concavity (E) ; postaxial and ventral 

 to the knob is a large basin-shaped concavity (B), followed by a ■ 

 ridge, and that again by a concave surface (G), having its post- 

 axial, and a portion of the ventral, margin so raised that its articular 

 surface is oblique to the main articulation. This surface comprises 

 the postaxial moiety of the articulation. The knob (A) fits into 

 the nit or socket on the preaxial side of the distal end of the ulna 

 (Pl/XXXIX, fig. 7, A). The concavity (B) articulates with the- 



