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FOSSIL REPTILIA OF THE 



with the centrum, and this, retaining its length, as in the sacral and lumbar region has 

 diminished by loss of transverse and vertical extent. The under surface is canaliculate 

 (fig. 7), and both the anterior and posterior expanded ends of the boundary ridges of the 

 lower groove have articular surfaces, h, h, for a haemal arch. 



In Plate I, fig. 9, the compressed subtriangular portion of an abdominal sternum (?) 

 is marked hs ; the pair of abdominal ribs which articulate by expanded thinned-off 

 ends to the sides of hs are marked h, h. 



The ungual phalanx (ib., figs. 12, 13) is remarkable for its degree of curvature, its 

 strong lever-process, and the deep lateral grooves. 



The value of this little specimen and fruit of Mr. Fox's persevering researches in 

 the Wealden deposits of his vicinity is its demonstration of the limited crocodilian 

 number of trunk-vertebrae deprived of reciprocal motion upon each other, and with 

 transverse processes thickened and terminally expanded for junction with the pelvis. 



1 repeat, with some stress, this character because the experienced and accomplished 

 palaeontologist of the United States, Joseph Leidy, M.D., while rightly recognising the 

 " half of a vertebral body " from a Cretaceous formation at Middle Park, Colorado, as 

 of a Poikilopleuron, remarks : — " Poicilopleuron was probably a semi-aquatic Dino- 

 saurian, an animal equally capable of living on land or in water, and perhaps spending 

 most of its time on shores or in marshes." 1 



But the cited capacity is enjoyed by Crocodilia equally with Dinosauria ; and 

 Poikilopleuron may well have spent, like its neighbour and contemporary Teleosaurus, 

 least of its time on shores or in marshes, if the latter were accessible to it in its Oolitic or 

 Cretaceous localities. 



The fossil described and figured by Leidy adds nothing to the evidence previously 

 extant of the affinities of Poikilopleuron ; and if I plead for the retention of the 

 orthography of the estimable discoverer of the genus, I more strongly protest against the 

 addition of a new generic term for which Leidy's fossil yields not a single character. 2 



The geological conditions under which Deslongchamps discovered his Poikilopleuron 

 led him to remark : " aussi dut-il passer une grande partie de sa vie dans les eaux et 

 probablement dans les eaux marines : puisque ses os sont restes dans un calcaire qui 

 doit evidemment sa formation a des debris marins." 3 



Amongst the rounded pebbles discovered in a position suggestive of their having 

 been in the stomach of the Poikilopleuron, as such pebbles are commonly found in the 

 stomach of a Crocodile or Alligator, Deslongchamps detected the tooth of a Cestraciont 

 Fish, 4 very significative of the element whence the Poikilopleuron derived its food. 



Our actual knowledge of the skeleton of Poikilopleuron is sufficiently complete to 



: ' Contributions to the Extinct Vertebrate Fauna of the Western Territories,' p. 268, 4to, 18/3. 



2 Ibid., pi. xv, figs. 16 — 18, " Antrodemus." 



3 Op. cit,, p. 51. 



4 Mem. cit., p. 65, " elle provient tres-probablement d'une des derniers proies qu'il avait avalees." 



