Smithsonian miscellaneous collections . - of the facet for the radius,for articulation with the lunar. Along the distal margin of the externalsurface, the scaphoid exhibits a slender facet for the centrale. Distallythe scaphoid shows a large and nearly rectangular facet, slightly con-cave dorsally and convex palmad, for the trapezium. The palmar sur-face and the palmar portion of the medial surface of the scaphoid pro- NO. 10 TILLODONTIA—GAZIN 83 jcct prominently to form a deep, transversely elongate, and smoothlyrounded process presumably having a ligamentous attachment. The scaphoid of the l
Smithsonian miscellaneous collections . - of the facet for the radius,for articulation with the lunar. Along the distal margin of the externalsurface, the scaphoid exhibits a slender facet for the centrale. Distallythe scaphoid shows a large and nearly rectangular facet, slightly con-cave dorsally and convex palmad, for the trapezium. The palmar sur-face and the palmar portion of the medial surface of the scaphoid pro- NO. 10 TILLODONTIA—GAZIN 83 jcct prominently to form a deep, transversely elongate, and smoothlyrounded process presumably having a ligamentous attachment. The scaphoid of the listhonyx specimen (fig. 34) would appear tobe much like that in Trogosus except that it is relatively wider trans-versely, and the proximal articular surface for the radius is relativelywider and more convex Fig. 33.—Trogosus hyracoides (Marsh) : Left carpals, metacarpals, and distalphalanx ( No. 17886) ; a, proximal (above) and distal (below) viewsof scaphoid, lunar, cuneiform, and pisiform; b, proximal (above) and distal(below) views of trapezium, trapezoid, centrale (proximal only), magnum, andunciform; c, proximal view of metacarpals I to Y; d, medial view of distalphalanx of 2d digit; X §• Bridger (B) middle Eocene, Wyoming. Lunar.—The lunar of Trogosus is less wedgelike, as seen dorsally(fig. 33a), and more nearly rectangular, as seen in proximal and distalviews, than the scaphoid. Its surface for articulation with the radiuscovers the dorsal two-thirds to three-quarters of the proximal surface(about half in the dorsopalmad elongate lunar of Tillodon) and is con-vex transversely as well as in a dorsopalmar direction. The lateral andmedial surfaces are without facets for the cuneiform and , the lunar shows three subequal dorsopalmad elongate surfaces 8
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Keywords: ., bookauthorsm, bookcentury1800, bookdecade1860, booksubjectscience
