MTJE^NOSAFEUS. 



101 



facet looks less directly outwards than in the anterior dorsals ; the anterior face of the 

 processes is marked by a strong longitudinal ridge for muscle-attachment (text-fig. 54). 

 In the posterior dorsals (text-fig. 55) the transverse processes rapidly shorten and 

 pass down the arch to the lower end of the pedicle ; behind this in the sacral and 

 caudal regions no transverse processes are present, the ribs articulating directly with 

 facets at the sides of the centra. 



There are three or four sacral vertebrae (text-fig. 56), the centra of which become 

 more and more depressed, so that the transverse diameter of the oval articular end 

 is greater than the vertical diameter; at the same time they become shortened, a 



Text-fig. 56. 



Sacral vertebra and rib of Murcsnosaurns durobrivensis : A, from abore ; B, from left side ; 

 C, from front with rib. (E. 2863, | nat. size.) 



«./., facet on centrum for neural arcb ; a'.f., facet for neural arch on proximal end of sacral rib ; 

 *•./., facet for sacral rib ; s.r., sacral rib ; s.f., facet for attachment with ilium. 



process continued into the caudal series. The articular faces of the centra are nearly 

 flat with a central tubercle. The ventral face is evenly and gently convex from side to 

 side and is perforated laterally by a pair of foramina ; externally its middle portion 

 passes into the ventral surface of the prominence, which bears the deeply-cupped 

 surface (r.f.) for union with the sacral rib (s.r.) ; this surface is situated a little nearer 

 the posterior than the anterior end of the centrum and is continuous above Avith that 

 for union with the neural arch (a.f.) ; this surface also is deeply concave imd extends 



