42 crocodilia. 



Ordinal Position- Uncertain. 



Genus ORNITHODESMUS, Seeley \ 



The specimen on which this genus is founded is regarded by its 

 describer as probably Avian, although presenting certain indications 

 of affinity with Dinosauria. The impossibility of its belonging to 

 the present Order does not, however, appear to be proved. 



Ornithodesmus cluniculus, Seeley 2 . 

 Hob. Europe (England). 



R. 187. The imperfect sacrum ; from the Wealden of Brook, Isle of 

 {Fig.) Wight. The type ; figured by Seeley in the ' Quart. Journ. 

 Geol. Soc' vol. xliii. pi. xii. figs. 1-6. 



Fox Collection. Purchased, 1884. 



Order CROCODILIA 3 . 



Limbs and body lacertiform ; the former short ; the latter with a 

 dorsal armour of pitted, imbricated, dermal scutes. Vertebrae either 

 pro- or amphiccelous, with persistent neuro-central suture; rib- 

 facet in middle dorsal vertebras forming a " step " on the transverse 

 process ; cervical ribs with long antero-posterior processes ; dorsal 

 ribs usually with uncinate processes ; two vertebrae in sacrum ; 

 chevrons generally open superiorly. Cranium relatively large, with 

 component bones firmly united, and some of them usually sculptured ; 

 palatines and pterygoids uniting in middle line, and latter joined to 

 base of cranium and giving off processes to unite anteriorly with 

 vomers; quadrate wedged in among adjacent bones; tympanum 

 with three eustachian canals; usually no columella; mandibular 

 symphysis uniting by suture ; no ossifications in sclerotic. Teeth 

 pointed and subconical or compressed ; inserted in distinct sockets. 

 Sternum cartilaginous ; an interclavicle ; usually no clavicle. Limb- 

 bones solid. Coracoid long or short, with fontanelle ; humerus 

 with head imperfectly differentiated from tuberosities and trans- 

 versely extended, with the deltoid crest terminating abruptly. 

 Ilium (fig. 7) without distinct pubic or preacetabular processes; 



1 Quart. Journ. Geol. Soc. vol. xliii. p. 206 (1887). 2 Loc. cit. 



3 Some of the following characters may not be applicable to the Aetosauria, 

 which are included by Baur (Sitz. ges. Morph. Munch, vol. iii. p. 55, 1887) 

 in this Order. 





