628 BRITISH FOSSIL REPTILES. 



Caen Oolite. Besides the Tilgate locality I was able to note, after examination of a 

 series of fossils belonging to S. H. Christie, Esq., from the siibmergecl AVealden Beds, 

 Isle of Wight, the " half of a dorsal vertebra from Brook Bay, which agrees in size, in 

 the form of the articular extremity, in the degree of median constriction, and especially in 

 the large size of the medullary" (chondrosal) " cavity at the middle of the bone, with the 

 vertebral characters of Poikilopleuron."* 



Species. Poikilo2)leuron pusillus, Ow. (' Crocodilia,' Plate 39.) 



This species is, to me at present, represented by eight vertebras, an ungual phalanx 

 of the rapacious type, and part of a medial symmetrical bone to which are articulated 

 portions of a pair of rib-like bones, as to the nature of which the nearest guess I can 

 make is that they represent part of the series of abdominal ribs with their sternum. 



All these bones show a compact osseous texture with a smooth or polished exterior, 

 and a section of one of the dorsal centrums exposed, what a fractured caudal one 

 indicated, viz. a large central chondrosal vacuity, such as characterises the centrum of 

 the Oolitic crocodilian genus Poikilopleiiron of Eudes-Dcslongchamps. 



The reptile, of which the present are fossilised remains, was discovered by the Rev. 

 W. Eox, M.A,, in the south-west Wealden of the Isle of Wight ; it is much smaller 

 than the type of the genus Foikilopleurou from the Caen Oolite, or the Wealden \ertebr3e 

 above referred to Poik. Bucklandi. It may be objected that the present specimens are 

 from a young individual of the same species ; but they show no signs of immaturity, and 

 the caudal hypapophyscs indicate the bases of the piers of the haemal arch not to have 

 been confluent as in the Poikilopleuron Bucklandi, and as in Igiianodon. 



The vertebral centrums are long in proportion, to their breadth and depth, and 

 the non-articular surface is so concave lengthwise as to give the appearance of the 

 centrum being constricted between the terminal articular surfaces. These arc almost 

 flat. 



In one trunk-vertebra, the sides of the centrum converge to a carinate inferior surface. 

 In another (Plate 39, flgs. 1 — 3) that surface is less narrow (ib., fig. 2). In both 

 the suture of the neural arch is traceable, but the arch has remained attached : it shows 

 a small facet (fig. 1, p) for the head of the rib at the fore part of the base of the neur- 

 apophysis. A horizontal (diapophysial) ridge (ib. d) extends from the prezygapophysis to 

 the upper surface of the postzygapophysis, broadening as it recedes. The neural spine is 

 compressed, but rises from nearly the entire length of the neural arch. The outer 

 surface of the centrum is compact, smooth, and glistening; and on making a vertical 

 longitudinal section the more definite generic character of the large chondrosal vacuity 

 was exposed, as in fig. 3, ch, 3. 



* ' Reports of t!ie British Association,' 1841, p. 84. 



