244 PEOFESSOE OWEN ON THE GENUS DINOENIS. 



in. lin. 



Breadth (across fore end) 2 7 



„ (across hind end) 2 2 



Depth, or vertical diameter, anteriorly 3 



„ posteriorly, including ischium and pubis ... 4 3 



,, of ischium, distal end 2 



Vertical diameter of acetabulum 16 



Horizontal diameter, including trochanterian surface . 2 1 



The pelvis includes, as in otlier birds, the parts corresponding to sacrum, ilia, ischia, 

 and pubes in mammals, but all coalesced into one mass or bone. 



The sacrum includes eighteen vertebrae. 



The ribs of the first or foremost (s i) have not coalesced with the centrum and neural 

 arch ; the articular surfaces for these elements are distinct on each side. The ribs of 

 the second sacral (PI. LIV. fig. l,pl. 2) are confluent by both head and tubercle; and 

 the body of the rib arches outward and downward for an extent of 2 inches 9 lines from 

 the tubercular confluence. 



The ankylosed ribs (ib. jj/. 3) of tlie third sacral vertebra project freely for about 

 5 lines from their coalesced tubercle. The pleurapophyses of the fourth, fifth, and 

 sixth sacrals consist of the ' head ' and ' neck ' only, the fourth terminating in a slightly 

 prominent ridge, the others expanding at both ends, one confluent with its parapo- 

 physis, the other with the ilium. The pleurapophyses of the sixth and seventh sacrals 

 have coalesced into one short and thick process, slightly expanded at the distal end, 

 which blends with the confluent acetabular or proximal ends of the ischium and pubis. 



In the eighth, ninth, and tenth sacrals the parapophyses and costal elements are 

 absent ; they abruptly reappear in the eleventh and twelfth sacrals, and coalesce with 

 each other at their respective distal extremities ; the proximal ones are coextensive 

 with the two centrums, the distal ends expand into a thick mass abutting against and 

 confluent with the inner or central surface of the posterior or trochanterian tract of 

 the acetabulum. 



A plate of bone extends from the hind border of the thirteenth pleurapophysis, and 

 expands as it extends outward and backward to coalesce with the mesial and under 

 margin of the ilium. The pleurapophyses of the fourteenth to sixteenth sacrals 

 have a similar course, outward, backward, and slightly upward, with similar expanded 

 abutments against the ilium, increasing in thickness and decreasing in length as they 

 recede in position. The corresponding coalesced processes of the two last (seventeenth 

 and eighteenth) sacral vertebrse are the shortest and thickest ; and their distal, sutural, 

 iliac connexions are not wholly obliterated. 



The breadth of the first sacral centrum (PI. LIV. fig. 1, 5i) midway between its 

 articular ends is 1 inch ; this dimension gradually increases to 1 inch 5 lines in the 

 fifth sacral (ib. s); it suddenly diminishes to 11 lines in the eighth vertebra (ib. 8), 



