ON BRITISH FOSSIL REPTILES. 75 



a strong process extends on each side outwards, and curves slightly backwards 

 parallel with the ex-occipitals, to join the mastoid and tympanic bones, the 

 latter of which expands as it descends to form the joint for the lower jaw. 



Feet. In. Lines. 



Breadth of posterior part of skull 100 



Length of parietal crest 060 



Breadth of the interorbital space 032 



Antero-posterior diameter of the middle of tympanic pedicle 2 5 



Vertical diameter of orbit 020 



Antero-posterior of orbit 030 



From lower margin of orbit to alveolar border 13 



From these dimensions it may be calculated that the entire length of the skull 

 must have exceeded 4 feet 6 inches. 



The skull of one of the Caen Teleosauri measures 3 feet 4 inches, whence 

 Cuvier calculates the entire length of the animal at near 15 feet. The Whitby 

 Teleosaur agrees with the Caen species, and differs from the Gavial in the 

 following particulars : the anterior frontal is less extended upon the cheek ; 

 the lachrymal is much more extended, and is larger at its base; the jugal 

 bone is more slender. The posterior fi'ontal, which separates the temporal 

 from the orbital cavities, is much longer and narrower. The parietal and oc- 

 cipital crests each form a thin trenchant plate, and are not flattened above. 

 The mastoidean angle is not uninterruptedly united with the back part of 

 the articular process of the tympanic, it is separated from it by a large de- 

 pression, which is overarched by a trenchant crest belonging to the ex-occi- 

 pital. The mastoidean bone has a concavity at its descending part, of which 

 there is no trace in the Gavial. The indentation between the articular pro- 

 cess of the tympanic, and the tuberosity of the basi-occipital is much smaller 

 than in the Gavial, and the basilar tuberosity projects downwards in a less 

 degree. The pterygoid ala is not expanded externally, as in all Crocodiles, 

 but is contracted by a large fissure, at the part where it goes to unite itself 

 to the bone ; the orbital margin of the malar is not raised, and does not leave 

 behind it a deep fissure as in the Gavial. The malar does not rise to join the 

 posterior frontal bone; but, on the contrary, the frontal descends to join the 

 malar at the external margin of the orbit. The vacuity between the orbit and 

 the anterior part of the tympanum is much elongated in the fossil, and occu- 

 pies four-fifths of the temporal fossa ; the anterior part of this fossa is narrow 

 and acute. The columella or ossicle of the ear is cylindrical, and much larger 

 in proportion than in any known Crocodile or other reptile. 



Cuvier calculates the number of teeth in the Teleosaurus Cadomensis to be 



180, viz. '-f^. 



The Teleosaurus Chcqmmnni has at least 140 teeth. 



The Gavial has 112, or ^|5ii- 



The teeth of the Whitby Teleosaur are as slender and sharp-pointed, but 

 not so compressed, as in the Gavial ; they correspond with those of the Caen 

 Teleosaur, and equally illustrate the dental characters usually attributed to 

 the present extinct genus*. 



The Whitby Teleosaur differs f>-om the Caen Teleosaur, as does the 



* M. H. V. Meyer refers to the genus Teleosaurus (Palicologica, p. 115) tlie thick obtuse 

 teeth of the Wealden or Sussex Crocodile figured by Dr. Mantell in his ' Illustrations of the 

 GeologN- of Sussex,' at pi. v. figs. 1, 2, 7, 9, 10, and 12. These teeth, however, belong to 

 Goniopholis, as docs also the scute figured in pi. vi. fig. 8 ; and they are accompanied with 

 deviations from the characters of Teleosaurus in the skeleton as striking as those which are 

 manifested in their own robust and obtuse figure. 



