130 REPORT— 1841. 



not include this characteristic part of the skeleton ; it does not form part of 

 the series of bones obtained by Mr. Holmes from the Wealden Quarry at 

 Horsham ; but in the collection of rolled bones of the great Wealden Sau- 

 rians — Cetiosaurus, Streptospondylus, and Iguanodon — in the museum of 

 Mr. SauU, there is a fine specimen of the sacrum with one of the iliac bones 

 attached, which, in the proportions of the vertebrae and the form of the ilium, 

 agrees with the known characters of the Iguanodon. 



This instructive specimen consists of five vertebrae anchylosed together by 

 the articular surfaces of their bodies and by their spinous processes, which 

 seem to fonn a continuous thick median ridge of bone. The five vertebrae 

 measure 17 inches in length. The articular extremity of the terminal sacral 

 vertebra is very slightly concave and subcircular, measuring 3 inches in both 

 vertical and transverse diameter. The bodies of the dorsal vertebrae are com- 

 pressed at their middle part, and broader below than in the dorsal region, and 

 concave in the direction of their axis, the concavities being separated by the 

 broad prominent convex transverse ridges formed by the anchylosed and os- 

 sified intervertebral spaces. The contour of the under part of the sacrum 

 thus forms an undulating line. The lateral and inferior surfaces are separated 

 by a more angular prominence of the centrum, the under surface is less con- 

 vex transversely, and the whole centrum is shorter in proportion to its depth 

 and breadth, than in the Megalosaurus. The neurapophyses present the same 

 remarkable modification in regard to their relations to the body of the ver- 

 tebra as in the Megalosaurus, having shifted their position from the upper 

 surface of a single centrum to the interspace of two, resting on proportions 

 of these, which are more nearly equal, as the vertebrae are nearer the middle 

 of the sacrum. The nerves were compelled therefore to escape from the 

 spinal canal over the body of the vertebra, more or less near its middle, and 

 they impress the upper surface there with a smooth canal. 



The strong, vertically compressed, transverse processes, or sacral ribs, rise 

 from the bases of the neurapophyses, and their origin extends upwards upon 

 the Ispine, and downwards upon the sides of the contiguous vertebral bodies 

 and intervertebral space; in the specimen described they are firmly anchy- 

 losed to all these parts, extend outwards and expand at their extremities, four 

 of which meet, join, and form an elongated tract of varying breadth to which 

 the ilium is firmly attached. The length of the largest penultimate transverse 

 process was 5 inches 8 lines, its vertical breadth at the middle 3 inches, its 

 thickness here 1 inch. The adjoining (last) transverse process was 5 inches 

 in length ; the interspaces of the transverse processes equalled from 2\ inches 

 to 2 inches. The sacrum increases in breadth posteriorly ; its transverse dia- 

 meter, including the anchylosed ilia taken at the posterior part of the ace- 

 tabulum, is 13 inches, at the anterior part of the sacrum only 8 inches. The 

 proportion of the spine thus grasped, as it were, by the iliac bones, which 

 transmit the weight of the body upon the thigh-bones, corresponds with the 

 mass which is to be sustained and moved ; and the size and structure of the 

 sacrum indicate, with those of the femur and tibia, the adaptation of the 

 present great herbivorous Saurian for terrestrial life. 



No. ^, Mantellian Collection, is the centrum of a sacral vertebra of a sub- 

 quadrate form, with a broad and flattened inferior surface, slightly concave 

 antero-posteriorly. The upper surface is excavated by a wide and moderately 

 deep canal, indicating the unusual size, for Reptiles, of the sacral portion of 

 the spinal chord. The anterior and posterior parts of the sides of this cen- 

 trum are raised, so as to form projecting sub-triangular rough articular sur- 

 faces, continued upon the margins of the spinal canal, evidently for the at- 

 tachment of the neurapophyses and the heads of the strong sacral ribs. The 



