Page:Notes on Osteology of Baptanodon. With a Description of a New Species.pdf/11

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a = approximate, b = broken.

The elements of the pectoral girdle of No. 919 are finely preserved and entirely free from distortion. The scapulæ lack about half of their upper free ends and the coracoids their posterior borders. (See Plate XXXVIII.) These missing parts have been restored from the pectoral girdle of B. discus, No. 878 in the Carnegie Museum.

The coracoids are broad subquadrangular bones winch join one another medially by large facets. The superior surfaces (Plate XXXVIII., Fig. 2) are flat-tened, although both elements are gently inclined toward the median line. The inferior surfaces are concave transversely and convex antero-posteriorly. The lateral borders are especially thickened forming a heavy articular face for the scapulæ and humeri. This outer articular end is divided into two unequal faces meeting in an obtuse angle. The more anterior and smaller one of the two is for the scapula, and looks outward, forward, and obliquely upward. The larger and posterior surface forms the greater part of the cavity. This border is much straighter and longer antero-posteriorly than on the coracoids of B. discus. It is very slightly convex from above downward and is covered with -like eminences. This articular end is supported by a broad neck formed by a deep -notch on the anterior margin. The anterior border from the inner notch thickens rapidly as it recedes posteriorly to form the intercoracoidal facet. (See Plate XXXVIII., Fig. 1.)

The scapulæ are moderately long bones the upper halves being narrow with nearly parallel sides, the articular end is broadly expanded antero-posteriorly and thickened on their posterior margins where they enter into the formation of the glenoid cavity. The articulating face for the coracoid joins this border at an.

The scapulæ extend outward, upward, and forward. Viewed longitudinally the inner surface is slightly concave. as they curve up to lap over the side of the ribs. The articular ends on the dorsal surfaces are concave antero-posteriorlv.