Wright and Huxley— Fossil Reptiles from Ireland. 167 



tiie neural spines and chevron bones of the caudal vertebrae, ■which 

 must have conferred upon the tail great power as a natatorial organ. 



The tail is not less than nine times the length of the head, 

 and is composed of, at lowest, seventy-five vertebra. Throughout 

 the anterior three-fourths of the tail, the centra of the vertebrae 

 are short and bi-concave ; but their neural spines and chevron 

 bones are produced into long flattened plates of bone, narrower 

 at their attached than at their free ends, where the bony sub- 

 stance becomes longitudinally grooved, and, as it were, frayed out. 

 The height of one of these vertebras, from the upper edge of its neural 

 spine to the lower edge of its chevron bone (which is continuously 

 ossified into the middle of its under face) , is three times as great as 

 the length of its centrum. 



In the body the neural spines shorten greatly, their height not 

 exceeding the vertical diameter of their centre; but they retain 

 their antero -posterior elongation. 



The number of vertebrae in the body cannot at present be ascer- 

 tained with certainty. That they were not fewer than ninety is 

 clear, but they may have been much more numerous. 



The skull is broad and short, and is about 1.2 inches long 

 in a specimen, the tail of which exceeds twelve inches in length. 



Both the hind and fore limbs are completely developed, though 

 small, and the posterior member is longer than the anterior. The 

 hiad limb, from the head of the femur to the extremities of the digits, 

 nearly equals the centra of six anterior caudal vertebrae in length, 

 or 1*5. There are five well-developed long and slender digits; 

 but the carpus does not seem to have been ossified. The fore limb 

 is not fully preserved, but it would appear to have resembled the 

 hind limb. 



The ventral surface of the body is provided with an armour of 

 dermal ossifications, of an oat-like or spindle-shape, and each about 0'2 

 in. long by 0*05 in. broad. 



We propose to confer upon the species, upon which the above 

 description is based, the title of Urocordylus Wandesfordii, after 

 Mr. Wandesford, the lord of the soil of the colliery from which it 

 was obtained. 



2. OpMderpeton. — When the peculiar caudal vertebrae of Urocordylus 

 were first discovered they were, for the most part, unconnected, not 

 only with body vertebrse, or skulls, but with any other remains. 

 Only in one instance did a series of such vertebra present, at 

 its anterior end (where it was obviously about to pass into the 

 body, which was unfortunately broken away), a number of scat- 

 tered oat-shaped dermal ossicles. 



At the same time, however, certain slabs exhibited skulls, followed 

 by long series of dorso-lumbar vertebrae and ribs, with a very com- 

 plete ventral dermal armour, composed of elongated and oat-shaped 

 ossicles. Thus one was naturally led to combine these disjoined 

 anterior and posterior fragments, which seemed to be identified 

 by their common armour. But it turned out, on strict comparison, 

 that the ossicles of the anterior fragments, which are termed 



