MUEtENOSAUEUS. Ill 



The coracoids (text-figs. G2, 67, 68) are very large and broad plates of bone, thin 

 posteriorly, with a much thickened region between the glenoid cavities, the thickening 

 being indicated on the visceral surface by a strong antero-posterior convexity. 

 Internally the two bones unite with one another in the middle line in a long suture, 

 which, in the adult, is continued forwards between the anterior median prolongations 

 of the bones till it becomes continuous with the symphysis of the scapulae. In its 

 posterior portion the symphysial surface is thin, but at the thickened portion of the 

 bone it widens out, again narrowing a little between the anterior prolongations, which 

 are approximately semicircular in section like the posterior processes of the scapulse. 

 The form of the posterior border of the bone is best understood from the figures. The 

 postero-lateral processes do not seem to develop till late in life {cf. text-fig. 62) 

 and never attain the strong development found in the coracoids of Cryiitocleidus. The 

 outer border is evenly concave and towards the middle is sharp-edged, thickening 

 anteriorly and posteriorly. Anteriorly it terminates on the hinder angle of the broad 

 o'lenoid surface which looks outwards and forwards and is half an oval in outline, the 

 line of junction with the glenoid surface of the scapula being the short diameter of 

 the oval ; this surface is very slightly concave, and in large individuals nearly smooth. 

 The facet for articulation with the head of the scapula looks outwards and forwards, 

 making an angle of about 135° with the glenoid surface; it is triangular and much 

 roughened. The anterior edge of the bone forming the posterior border of the coraco- 

 scapular opening is thin and sharp. 



Fore Limb (PI. IV. fig. 7; PI. V. fig. 11; text-fig. 63, B).— The fore limb is 

 considerably larger than the hind limb *, and the distal end of the humerus is more 

 expanded than that of the femur. In older individuals of the larger species 

 {M. durohrivensis, PI. V. fig. 11) the humerus may become extremely massive and 

 the distal end proportionately wider, although there is no approach to the great 

 expansion seen in the humerus of Cryptocleidus. The upper end is considerablv 

 enlarged and bears the head and the great tuberosity, which is situated on the 

 dorsal surface a little towards the posterior side. The head does not seem to have 

 ever become fully ossified, the surface even in the oldest individuals being only 

 slightly convex and covered Avith rugosities and tubercles, which seem to indicate 

 that a considerable capping of cartilage was present, a conclusion which is supported 

 by the form of the glenoid cavity ; probably the cartilage-covered head was nearly 

 hemispherical. Above and posteriorly the cartilage-covered surface of the head is 

 continuous with that forming the upper end of the great tuberosity, the two surfaces 

 making a slight angle with one another. The upper end of the tuberosity is 

 roughly oblong in outline, its outer angle forming strong prominences; from the 



* la the original description of Murcenosauriis leeclsi it is stated that the fore limb is the smaller, but 

 the paddle described is reaUy the hind limb (Quart. Journ. Geol. See. vol. xxs. (1S74) p. 207). 



