412 Mr. Owen's Description of the Remains of a Bird, 



merus, is nearly the same as in the skeleton of the Albatross ; and there is no 

 bird now known, north of the equator, with which the fossils can be compared. 



All the three fossils exhibit the thin compact external walls and large air-cavities 

 which characterise the texture of the corresponding bones in birds of flight. 



Description of the Remains of a Chelonian Reptile from the Chalk, PI. XXXIX. fig. 5. 



The remains of the Chelonian reptile were discovered in the lower chalk at Bur- 

 ham, in Kent. They consist of a few of the marginal plates of the carapace and 

 some smaller fragments of the expanded ribs which form the dorsal bony shield. 

 The marginal plates are four in number, united together by the usual finely in- 

 dented sutures, and each impressed along its middle and upper surface with a line 

 corresponding to the margin of the horny plate that originally defended it. The 

 external or free margin of each plate is slightly emarginate in the middle. These 

 marginal plates are narrower in proportion to their length than in the Chelone My- 

 das and Chelone imbricata, and they deviate still more, in the character of their in- 

 ternal articular margin, from the corresponding plates of the terrestrial Chelonia ; 

 but they sufficiently agree with the marginal plates of the carapace of the Emydes 

 to render it probable that the present chalk fossil is referable to that family of 

 Chelonia which lives in fresh waters or estuaries*. 



Description of the Vertebral Column of a small Lacertine Saurian from the Chalk. 



PI. XXXIX. fig. 3 and 4. 



The third fossil from the chalk which I have to notice, is one which Sir Philip 

 Egerton has recently added to his collection ; it consists of a chain of small vertebrae 

 in their natural relative position (fig. 4.). The bodies of these vertebrae are united by 

 ball- and socket-joints, the socket being on the anterior, and the ball on the posterior 

 part of the vertebra ; and they are proved to belong to the Saurian class of reptiles by 

 the presence of many long and slender ribs, and by the conversion of two vertebrae 

 through the length and strength of their transverse processes into a sacrum. Re- 

 mains of an ischium and pubis are connected with the left side of this sacrum, 

 proving incontestably that this reptile had hinder extremities as well developed as 

 in the generality of Saurians ; but of these, as well as of the anterior extremities 

 and head, there is no trace. 



* Subsequent observation of the modifications in the form of the marginal plates and of other parts 

 of the skeleton of extinct Chelones, by which the interval separating the existing marine and freshwater 

 species is diminished, has weakened the impression which the character of the marginal plates of the 

 chalk Chelonite first made in favour of its Emydian affinities ; and the examination of the nearly entire 

 skeleton of the same species recently obtained from the same quarries at Burham by Mr. Bensted, and 

 ■described since the reading of the present paper by Dr. Mantell in the Philosophical Transactions, has 

 demonstrated that it is not an Ernys, but a true Chelone, or marine Turtle.— April 1842. 



