116 BRITISH FOSSIL REPTILES. 



The skull yielding the above dimensions is much smaller than that of the Crocodilus 

 toliapicus, PI. 2 i? ; but it cannot have belonged to a younger individual of the same 

 species, because, in existing Crocodiles, the part of the skull anterior to the orbits is 

 proportionally shorter in the young than in the old individuals, as may be seen by 

 comparing the figures which Cuvier has given of the skulls of three individuals of 

 different ages of the Crocodilus biporcatus, in figures 4, 18, and 19, of plate 1 of the last 

 volume of the ' Ossemens Fossiles ;' whereas the part of the skull anterior to the orbits 

 is relatively longer and more slender in the smaller fossil skull now described than in 

 the larger one on which the species Croc. toUajncus is founded. We have, therefore, 

 satisfactory proof that two species of true Crocodile existed during the deposition of 

 the Eocene Clay at the actual mouth of the Thames, and have left their remains in 

 that locality. 



Their specific distinction is further illustrated by the different forms and propor- 

 tions of particular parts of the skull. The alveolar border is more nearly straight; the 

 transverse expansion of the maxillaries (21) is less, whilst that of the premaxillaries 

 (22) is greater : the interorbital space is broader and more concave. The teeth are 

 more uniform in size, are more regularly spaced, and are wider apart : they are, likewise, 

 upon the whole, larger in proportion to the size of the jaw. Figure 5, PI. 2 A, shows 

 the crown of a new tooth just emerging from the second socket of the maxillary bone 

 of the natural size ; figure 6 is the fourth tooth of the premaxillary, fully formed ; fig. 7 

 is the displaced tooth which is cemented by the matrix to the palatal surface of the 

 premaxillary in fig. 2. The enamelled crown shows the fine raised longitudinal ridges 

 better developed than one usually sees them in modern Crocodiles. There are twenty- 

 one alveoli on each side of the upper jaw. 



In all the particulars in which the skull under description differs from that of the 

 Crocodilus toliapicus, it departs further from the nilotic crocodile, and resembles more 

 the Gavial-like Crocodile of Borneo ; and as one of the old Egyptian names of the 

 Crocodile, Champsa, has been applied generically to the Gavials by some recent 

 Erpetologists, I have adopted the term ' Champsoides' to signify the resemblance of 

 the present extinct species of Eocene Crocodile to the Gavials. 



The basioccipital condyle, together with the condyloid processes of the exoccipital, 

 project backwards in the Croc, champsoides farther than in any modern Crocodile ; and 

 the supraoccipital 3, fig. 4, PI. 2 A, descends nearer to the foramen magnum. 



The upper jaw is more depressed, and the suborbital part of the maxillary bone 

 is much less inclined to the vertical in the present skull than in the original of Dr. 

 Buckland's figure of the Crocodilus Spenceri, which in other respects more nearly 

 resembles the Croc, champsoides than the Croc, toliapicus ; the difference above specified 

 seems to be greater than can be accounted for by any accidental pressure to which 

 the fossil skull figured in PL 2 A can have been subjected. The mutilated skull to 

 which the term Croc. Spenceri was originally applied, is defective, as I have said, in the 



