OPHTHALMOSAUEUS. 49 



tliat the union with the clavicle may have extended to this deflected portion, which 

 Professor Seeley regards as equivalent to the acromion process. The ventral surface is 

 concave from before backwards. The blade is narrow and is slightly curved upwards ; 

 it is nearly the same width throughout, widening only a little towards its upper end, 

 which is truncated nearly at right angles by a surface which seems to have borne a 

 cartilaginous lip or suprascapular cartilage in life. The anterior, slightly concave 

 border of the blade is rounded from above downwards, and the lower portion of its 

 inferior edge bears a long roughened surface for union with the clavicles ; in some 

 cases the roughened area at this point is so marked that it forms a slight projection, 

 which might perhaps be regarded as a sort of acromion process. The posterior border 

 of the blade is also roughened, presumably for the insertion of muscles. 



The clavicular arch (text-fig. 34) consists of a pair of clavicles and a T-shaped inter- 

 clavicle. The clavicles (text-fig. 34, A, B, C) are long curved elements terminating 

 externally in a point and internally in a complex and irregular sutural border, by 

 which they interdigitate and unite more or less firmly in the middle line, being 

 further keyed together by the anterior bar of the interclavicle. The external portion 

 is more or less oval in section and bears on its posterior side a roughened surface for 

 ligamentous union with the corresponding surface on the front of the scapula above 

 referred to. Internal to this outer horn-like portion the bone widens out and consists 

 of a thickened anterior rim from which a thinner shelf-like region projects upwards 

 and backwards almost at right angles, the two forming the deeply grooved inner surface 

 to the bone (text-fig. 34, C, i.cl.g.). It is into this groove towards the median portion 

 of the bone that the arm of the T-shaped interclavicle fits, the union in some cases 

 being extremely close and perhaps in old individuals in places amounting to actual 

 fusion of the two elements. The antero-dorsal surface of the clavicle is smoothly 

 convex from before backwards in its outer portion, but towards the middle it bears 

 several strong ridges which terminate in the digitations of the median sutural surface. 

 The interclavicle (text-fig. 34, D, E, F) consists of an anterior transverse bar and a 

 posterior median process. The anterior portion thins away towards each end. 

 terminating in a blunt point. Dorsally it is deeply grooved like the clavicles, its 

 anterior nearly flat face making about a right angle with the rounded ventral portion, 

 which is raised in the middle into a roughened boss of bone : this remains uncovered 

 by the clavicles, which embrace the remainder of the ventral and the lower portion 

 of the anterior face of the transverse bar (text-fig. 34, D, F). The posterior bar has 

 its ventral face convex from side to side, while the dorsal is convex anteriorly, but 

 posteriorly bears an elongated flattened facet [cor.f.) which must have been applied 

 to the ventral surface of the intercoracoidal cartilage, or perhaps in old individuals to 

 the ventral surface of the coracoids themselves. 



The humerus (text-figs. 36 & 37) is a short but very massive bone, the upper end 

 being particularly solid, while the lower is compressed in the plane of the paddle. 



n 



