210 



CHELONIA. 



on the latter for the pubis. This portion of the specimen 

 (fig. 45) has been figured by the writer in the ' Quart. 

 Journ. Geol. Soc' vol. xlv. p. 517, fig. 4. No history. 



24816. The anterior extremity of the plastron ; from Swanage. 

 Both surfaces are exhibited. Purchased, 1849. 



35772. Slab exhibiting the ventral aspect of the plastron ; from the 

 Purbeck of Swanage. This specimen is rather narrower 

 than the preceding ; while the entoplastral is relatively 



Fig. 45. 



Pleurostemum bullocki. — Dorsal aspect of the posterior extremity of the plastron ; 

 from the Purbeck of Swanage, 5. hp.jp, hypoplastral ; xp, xiphiplastral ; 

 /, facet for pubis. 



less wide, and the lateral borders of the xiphiplastrals 

 are somewhat more emarginate. These differences cannot, 

 however, be regarded as of more than individual, or 

 perhaps sexual, value; the width of No. H. 911 lias 

 moreover been increased by pressure. Purchased, 18G0. 



28433. Slab showing the ventral aspect of the plastron of an im- 

 (Fi<j.) mature individual, together with three marginals of the 

 left side ; from the Purbeck of Swanage. Figured in 

 woodcut fig. 46. The great breadth of the entoplastral 

 is well shown. The middle region is not quite fully 

 ossified. Purchased, 1853. 



40846. Slab showing the ventral aspect of a plastron agreeing in 

 size with the preceding specimen, together with many of 

 the marginal bones of the carapace ; from Swanage. The 

 entoplastral is less wide than in the preceding specimen. 

 In the marked lateral emargination of the xiphiplastrals 

 and the contour of their terminal notch this specimen 

 closely accords with the type plastron of P. concinnwn. 



Purchased, 1867. 



