THE SKELETON OF TRIMERORHACHIS 295 



longest, measuring about 52 mm. They also have a considerable 

 curvature and are more or less expanded at their extremities. 

 With the tenth or eleventh they have decreased in length to 45 mm., 

 are less curved, and not dilated at their distal ends. Thence to 

 the tenth precaudal they are of uniform length, more slender, and 

 pointed. When seen from above these are all slender and nearly 

 straight, with a moderately expanded proximal end; when turned 

 upon their sides they are broader, somewhat curved, and with 

 a more dilated head. Apparently some of them at least have a 

 capitular prolongation in articulation with the intercentra. The 

 first two precaudal ribs are slender, pointed, and entirely free, 

 and about one inch in length. 



The right humerus lies near the angle of the right mandible, 

 as will be seen in the photograph, with its head directed forward, 

 and with the radius somewhat removed from its distal end. There 

 are no remains of the skin either above or below these bones. 

 Some half-dozen skulls of Trimerorhachis have now been obtained 

 with the peculiar clavicular girdle in position or nearly so, lying 

 more or less between the mandibles posteriorly. In the drawing 

 (Fig. 2) I have outlined in interrupted lines a clavicular girdle of 

 another skull of the same size as the present one, in position, 

 placing it farthest back of any of the connected specimens. The 

 angles of the clavicles with their ascending process must indicate 

 the position of the scapula and articulation of the humerus. The 

 scapula is hidden and not certainly determinable in this specimen, 

 though the edge of a protruding bone at the inner side of the distal 

 end of the humerus, as it lies in the matrix, is probably that of the 

 scapula. The scapula, ilium, and limbs of the left side are doubt- 

 less preserved in this specimen covered by the skin and matrix, 

 but it has not been thought wise to sacrifice so much of the speci- 

 men as might be necessary in the search for them. In all the 

 material from the bone-beds so far examined not a trace has been 

 found of hand or foot bones, so that nothing can be said of their 

 structure. 



The right ilium lies in place in the matrix, in a vertical position 

 opposite the ends of the first two presacral ribs. The bone is 

 relatively very small, as will be seen from the figure. Among the 



