630 BRITISH FOSSIL REPTILES. 



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

 palaeontologist of the United States, Joseph Leidy, ]\I.D., while rightly recognising the 

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

 of a Poikilo2}leuron, remarks : — " Poicilophuron was probably a semi-aqnatic 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."* 



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

 Toilcilophuron may well have spent, like its neighbour and contemporary the Telcosaurus, 

 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.f 



The geological conditions under which Dcslongchamps discovered his Poikilopleuron; 

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

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

 doit evidemment sa formation a des debris marins." j 



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

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

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

 Fi3h,§ very significative of the element whence the Poikilopleuron derived its food. 



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

 give the answer to the question, " Whether the cavernous structure of its skeleton was 

 related to pneumatic functions, as in Birds, flying Reptiles, and some others ?'' || The 

 central cavity is completely closed ; no pneumatic orifice or canal penetrates thereto : it 

 had no communication with pulmonary or other air-cells. Nor is the alternative limited 

 to marrow.^ Primitive " chondrine," to which ossification had not extended, most 

 probably filled the vacuity in the vertebral body shown at d, fig. 2, plate ii, of the 

 ' Memoires de la Societe Linneenne de Normandie,' sixieme volume, -ito, 1S38; as 

 in figures of Plate 39, and in fig. 16 of Leidy's plate xv, op. cit. 



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



t Ibid., pi. XV, figs. 16 — IS, " Antrodemus." 



\ Op. cit., p. 51. 



§ Mem. cit., p. 65, " elle provient tres-probablement d'uue des deruiers proies qu'il avait avalees." 



II Id., p. 279. 



\ " Dans les deux series, le corps des vertebres est creuse d'une grande cavite meduUaire (fig. 2 d, 

 et V. 6) ; le tissu spongieux n'existe qu'aux deux bouts ; il y a de chaque cote, dans la gouttiere laterale 

 un trou pour le passage des vaisseaux nourriciers," p. 78 ; " ces vertfebres presentent a I'interieure une 

 grande cavite meduUaire analogue a celle des os longs." Mem. cit., p. 83. 



