The transverse processes of the dorsal vertebræ, from the second to the sixth, are well developed and are bridged over with a thin layer of bone. The ventral spines are partly fused and form a very prominent and continuous ridge. (Fig. 11, No. _A_, 1, shows the fused superior spines; No. 2, the fused inferior spines; and No. 4, the intervertebral foramina.) =The Lumbo-sacral Vertebræ= (Fig. 5, Part II, No. 4). _Location._—The fused lumbo-sacral section of the spinal column forms the roof of the pelvic cavity. [Illustration: FIG. 11.—Bones from the scapular arch. _A._ Dorsal vertebra. 1, Superior spinous ridge, 2, Inferior spinous ridge. 3, Oblique processes. 4, Intervertebral foramina. 5, Articular facette for head of the rib. 6, Articular facette for tubercle of the rib. 7, Articular portion of the body. _B._ Outer surface of scapula. _C._ Inner surface of scapula. 1, Thin caudal end. 2, Articular head. 4, Processus furcularis. 5, Processus humeralis. 6, Processus coracoideus. _D._ Outer surface of coracoid. _E._ Inner surface of coracoid. 1, The furcular tuberosity. 2, Articular facette for articulation with the sternum. 3, Articular surface for humerus and scapula. _F._ Outer surface of humerus and G the inner surface of the same. 1, Trochanteric fossa. 2, Oval articular head at proximal end. 3, Shaft. 4, Distal end showing articular condyles. 5, Trochanter. 6, Trochlea for ulna. 7, Trochlea for radius. 8, Depression or fossa. _H._ Section through the median plane of the humerus showing the delicate cross partitions illustrating provisions made for bones provided with air-sac extensions. ] _Description._—The lumbo-sacral region consists of fourteen vertebræ which are distinct in the body of the newly hatched chick, but which become fused soon after hatching. With these vertebral segments there are fused the last dorsal and first coccygeal vertebral segments. This fusion is so complete that the segments are indicated only by the intervertebral foramina on the sides through which the spinal nerves pass, and by transverse markings on the inferior surface of the bodies. The lumbo-sacral vertebræ, called the sacrum, and the ilia are fused. The dorsal spines of the vertebral segments are indicated only in the anterior portion where they are fused, forming a plate. There are no prominent ventral spines. =The Coccygeal Vertebræ= (Fig. 4, No. 27). _Location._—The coccygeal or caudal vertebræ, or vertebræ coccygeæ, constitute the bones of the tail. _Description._—There are seven coccygeal vertebræ. The last segment, shaped like a plough share and therefore called the pygostyle, is the largest and is supposed to have been formed by the fusion of several original distinct segments. It supports the coccygeal oil gland and the row of rudder feathers, or rectrices, which are arranged fan-wise.