ATLANTOSAURIDiE. 



143 



vol. xliv. p. 58. The humerus has a length of 0,620 

 (24-5 inches) ; it has a proportionately much shorter 

 shaft than the humerus of Cetiosaurus ooconiensis, but 

 approximates to that type in its widely expanded head. 

 Possibly these specimens may be referable to Cetiosaurus 

 brevis ; but the specialized character, indicated by the 

 shortness of the humerus, may perhaps point to their 

 affinity with Titanosaurus, of which the procoelous caudal 

 vertebrae are evidently of a more specialized type than 

 those of other Sauropoda. On the other hand, these spe- 

 cimens may indicate a distinct genus. (See No. H. 722, 

 p. 246.) Mantell Collection. Purchased, 1853. 



2578. An imperfect right ilium ; from the Wealden of Cuckfield. 

 This specimen, which wants the two extremities, the 

 lower half of the acetabular portion, and the pubic process, 

 apparently approximates to the ilium of Morosaurus 

 (fig. 21), showing the same outward direction of the 

 upper half of the acetabular portion, and the deep con- 

 cavity of the external surface of the anterior part of 

 the body. Mantell Collection. Purchased, 1838. 



46017. A bone, wanting the distal extremity, which is probably 

 the right fibula; from Sandown, Isle of Wight. The 

 absence of a medullary cavity is shown. 



Pur chased, 1874. 



Family ATLANTOSAURID.E. 



Maxillary region of cranium much depressed. Cervical vertebrae 

 broad, of moderate length, with rim of posterior cup vertical ; 

 inferior surface of middle dorsal vertebrae broad and flat ; typically, 

 each sacral bearing its own arch, and the centrum hollowed ; 

 caudals typically with postzygapophyses ; chevrons closed, and 

 articulating by single facets. Distal extremity of scapula not 

 expanded ; humerus comparatively slender ; ischium (fig. 23) 

 directed downwards, with middle of acetabular portion on line of 

 axis of shaft, and latter broad and distally expanded. 



The transverse diameter of the caudal vertebrae exceeds the 

 vertical, and the neural canal is very large. 



The family name is taken from one of the American genera, 

 which, although of later date than Ornithopsis, was one of the first 

 well-defined forms. 



