METB10BHYNCHUS. 143 



Some approximate dimensions (in centimetres) of some of these vertebrae are : — 



Middle 

 Candals. Dorsals. First Second First Anterior eaurkls. Posterior 



, « s , » „ sacral, sacral. caudal, caudal. , "■ — s caudal. 



Length in mid- 

 ventral line . . . 5-9 6-2 6-5 6-8 5-8 5-9 5-1 6-8 GO 5-8 53 



Width of posterior 



face of centrum . 4-8 5-4 5-8 5-4 5-0 5-5 5-2 4-2 3-8 3-4 2-8 



Height of posterior 



face of centrum . 5-0 5-1 5-3 5-5 3-9 4-6 4-5 3-9 3'3 31 2-5 



Height to top of 

 neural spine . .11-0 14-1 12-8 13-1 12-3 11-5 app. .. 11*3 9-9 9-5 



Family GEOSAURIM. 



Mesosuchia which are modified for a strictly aquatic life. Nasals large, taking a 

 considerable share in the formation of the rostrum ; they may or may not extend 

 forwards to the premaxiliae. Prefrontals very large and overhanging the orbits, which 

 look forwards and outwards. Premaxiliae with no terminal expansion. Teeth usually 

 somewhat compressed and carinate. Vertebrae with slightly concave ends. Fore limb 

 greatly reduced and paddle-like. Hind limb large. Tail long, with the distal segment 

 sharply bent down and supporting a large dorsal fin. No dermal skeleton is known ; 

 a sclerotic ring was present in the eye. 



This family corresponds to the group Thalattosuchia of E. Fraas *. 



Genus METKIORHYNCHTTS, H. v. Meyer (emend. E. E. Deslongchamps). 



[Isis, 1830, pt. v. p. 518, and Palaeologica (1832), p. 106 ; emend. E. E. Deslongchamps 

 in Notes Paleontologiques, p. 132 (Caen, 1867).] 



1890. Suehodus, Lydekker, Quart. Journ. Geol. Soc. vol. xlvi. p. 288. 



Exhibiting the characters of the family, but distinguished from the later Qeosaurus 

 by (1) the absence of the serration of the carina? of the teeth, the enamel of which is, 

 as a rule, raised into a varying number of fine longitudinal ridges ; (2) the smaller 

 degree of reduction of the humerus ; (3) the greater length of the tibia and fibula in 

 comparison with the femur. Dacosaicrus, from Kimmeridgian beds, is very similar 

 and should perhaps be referred to this genus. 



Oxford Clay. The later forms are probably all referable to Geosaurus or Daoosaurus. 



This genus was founded by H. v. Meyer for Cuvier's " Second Gavial of Honfleur " f , 



*' " Die Meer-Crocodilier (Thalattosuchia) des oberen Jura," Paloeontographica, vol. xlis. (1902), p. 1. 

 t Ossements Fossiks, ed. 2, vol. v. pt. 2 (1824), p. 143. 



