18 



Dinosauria — Omosaurus. 



The skull shows many points of resemblance to that of 

 Igtianodon, especially by the presence of a predentary bone, but 

 it is lower and narrower and in this respect it resembles the 

 Scelidosaurian type. 



Wall-case, 

 No. 4. 



Omosaurus. 



Fig. 20. — Left lateral view of skull of Stei/osauriis stenojis (Marsh), \ natural size; from 

 the Upper Jurassic, S. Colorado, North America, a, nares; 6. orbit; c, lateral 

 temporal fossa ; pm, premaxiUa ; m, maxilla ; n, nasal ; pf, prefrontal ; ,«o, supra- 

 orbital ; fp, postfrontal : po, postorbital ; I, lachrymal ; j, jup;al ; q, quadrate ; sq, 

 squamosal; oc, occipital condyle; ar, articular; sa, surangular; a», angular; s, 

 splenial ; d, dentary ; ^x?, predentary (after Marsh). 



To this sub-order are referred the remains of a large Dinosaur 

 from the Kimmeridge Clay of Swindon, Wilts, described by Sir 

 Richard Owen in his Monograph on the Fossil Reptilia of the 

 Mesozoic Formations (PalEeontographical Society's Volume for 

 1875), under the name of Omosaurus armatus. The series com- 

 prises, in an immense block, the iliac bones of either side with 

 the entire sacrum, retaining the normal form and position, an 

 ischium, a femur, seA'eral dorsal and caudal vertebrae projecting 

 in bold relief from the background of grey stone, forming a 

 magnificent fossil group unique of its kind. 



In addition to the bones above mentioned (which are all 

 imbedded in one block 6' 0" X 7' 6"), a large dermal spine, 

 several centra and processes of many vertebrae and chevron- 

 bones, an entire humerus, ulna and radius with carpal and 

 metacarpal bones, all parts of the same fore-limb ; also a com- 

 plete ischium and pnbis, and six caudal vertebrae, were found 

 lying in the clay around the larger mass. 



The femur measiires more than 4 feet, and the humerus 

 is nearly 3 ft. in length and enormously broad. The head and 

 neck are unfortunately wanting, but thei*e is little doubt 

 that nearly the entire animal might have been obtained had 

 some competent person been present in the j^it when the 

 remains were first observed. 



Remains of another species of this genus (Omosaurus durob- 

 rivevsis) from the Oxford Clay of Peterborough, are also 

 exhibited in this case. 



