80 Transactions. — Zoology. 



Sternum. PI. XII., fig. 1, and XIII., figs. 1, 2. 



This bone is almost perfect, having lost only a few lines of its inferior 

 margin, and, though it difiers considerably from the characters attributed to it 

 by Professor Owen, this is, without doubt, due to his not having had a 

 connecteid fragment of the superior portion of the bone, so that its enormous 

 posterior concavity was not appreciated. It is chiefly remarkable for its 

 regular oblong shape, without any irregularities of outline or unossified. inter- 

 spaces. The texture must be cancellated, for, though apparently thick and 

 massive, it is very light in proportion to its size, as will be seen in the 

 appended table. Its general form is scaphoid, the concavity being very marked, 

 in the upper half, amounting to one inch in depth measured from a transverse 

 chord, and. to one-and-a-half inches in depth if measured from a longitudinal 

 chord ; the total length of the latter being 7 inches. The anteiior width at 

 the costal processes {a) is 4 inches, and at the posterior end of the costal 

 border 3 inches 6 lines. 



The costal border (e-e') occupies half the lateral margin of the bone, the 

 posterior half of the line being only slightly concave interiorly, and exteriorly 

 being flat in the middle and sloping very slightly to the inferior angles. The 

 superior margin is thin, and presents a wide mesial notch (f) and two lateral 

 notches (^), which are bounded exteriorly by the costal processes, which project 

 backwards and upwards for 6 lines. The coracoid grooves (6') are 1 inch 

 6 lines in length and 2 lines in depth of anterior border. They are separated by 

 a slight triangular interspace (f'J 5 lines wide, beneath which is a smaller 

 triangular pit (7t). The keel (c) commences by two angular ridges bounding 

 this pit posteriorly, and forms a blunt process 3 inches in length (c-c'), 

 expanded anteriorly to a rough tuberculate surface 4 lines in width and 9 in 

 length, and then compressed into a narrow tuberculate ridge that is gradually 

 lost in the smooth convex surface of the bone at less than one-half the distance 

 from its superior margin. The greatest elevation of the keel above the convex 

 surface of the bone is less than 3 lines. The impression (d) for the attachment 

 of the pectoral muscle extends from the exterior angle of the coracoid notch 

 towards the posterior part of the keel, including a triangular area which 

 occupies only one-sixth of the exterior surface of the bone, showing the 

 extremely limited and feeble attachment of the great muscles of flight. Large 

 pneumatic foi'amina (i) exist in the interior of the bone at the iipper 

 angles, and one (i') on the exterior surface on the left side only. 



FuRCULUM. PI. XII., figs. 2 and 3. 



The clavicles ai'e completely joined into a smooth, slightly-compressed 

 furculum, like that of the goose, except that the antei'o-posterior curvature is 

 confined to the articular processes, which diverge 1 inch above the genei-al 



