xi. MEGALOSAURUS VERTEBRAE. 205 



4-6 -inches, length 4-25, breadth 4-5. Elongated cavities are en- 

 closed in this bone, on the sides of the body. 



Sacrum (Diagram No. L1X. fig. i). The five vertebrae which, 

 anchylosed together, constitute the strong support of the hind legs, 

 retain somewhat of the lumbar character in the anterior, and of 

 caudal aspect in the posterior. The neural spines of the second, 

 third, and fourth are united above, separated below : this may also 

 have been the case with the others, and thus a strong continuous 

 vertical crest, twenty-one inches long, completed the fabric. The 

 whole is on a gentle curve, convex upward. The bodies of the 

 vertebrae are deeply constricted in the middle of their length, and 

 thickly annulated by revolution of the articular faces toward the 

 edges. Thus these coalescing edges combine into thick prominent 

 belts measuring an inch across. 



These belts rise upwards into strong though short transverse 

 processes, which are placed in a line convex downward, sinking 

 from the first and second toward the third and fourth, and then 

 rising upward to the fifth. The two anterior of these processes 

 are near together, the fourth and fifth far apart. Above them runs 

 a sort of horizontal cornice, formed on the line of the zygapophyses, 

 and above this are vertical arched plates, half as high as the neural 

 spine. Of these, two are very distinct above the third and fourth 

 transverse process: it is not clear whether they did exist in the 

 other corresponding spaces, but as something analogous appears 

 in the dorsal vertebrae, it seems a probable inference. 



The anterior zygapophysis is a linguiform projection with a 

 narrow mesial furrow below, and a broad concave receiving surface 

 above. The posterior zygapophysis is shaped to fit this hollow 

 by a broad projecting ledge above a horizontal notch and a narrow 

 triangular prominence. This arrangement is of the deinosaurian 

 type somewhat like iguanodon but quite diiferent from that of 

 teleosaurus, or steneosaurus, or living crocodiles. 



The neural canal, one inch in diameter, is not contracted in the 

 middle of the vertebrae ; it is longitudinally furrowed. Four hori- 

 zontal tubular passages for nerves lead from the great canal through 

 the three middle vertebrae, and constitute transverse tunnels about 

 five-eighths of an inch in diameter. Three of these, belonging to 

 the second, third, and fourth vertebrae, are open tubes ; that cor- 

 responding to the first vertebra is filled with stony matter. 



