86 
CHELONIA FROM THE 
CHELONIA 
FROM THE PURBECK SERIES OF SWANAGK, 
IN THE ISLE OF PURBECK. 
Exhibited on Shelves in the First Compartment on the 
South side in the West Room. 
1 Pleurosternon Sedgwicki. 
Perfect carapace, nuchal plate very slightly emarginate. 
Length 18f inches, breadth 15^ inches; resembles in 
aspect Pleurosternon ovatum, but is shorter and broader. 
The first neural plate subdivided, as in Pleurosternon 
concinnum and P. emarginatum, with posterior impres¬ 
sion of the first vertebral scute passing over the poste¬ 
rior part of the anterior subdivision. The second neural 
plate is narrow and four-sided. The eighth neural plate 
is j of an inch long, and the ninth, which widens behind, 
is 1^ inch long. The third, fifth, and ninth neural plates 
are crossed by vertebral scutes, as in Pleurosternon 
emarginatum. The first vertebral scute is narrower than 
the second and third, which are of equal width. The 
other characters approximate it to the species P. emar¬ 
ginatum and P. ovatum. The marginal plates are much 
broader than in the former species, and display no trace 
of the posterior emargination. The surface ornament is 
of the usual kind in Pleurosternon. 
2 Pleurosternon Yansittarti. 
Perfect carapace; presented by Augustus Arthur Van- 
Sittart, Esq. It resembles in aspect Pleurosternon emar¬ 
ginatum, but is broader in front. Length 19| inches, 
breadth 17| inches. The marginal plates and scutes are 
very broad. As in Pleurosternon ovatum and P. lati- 
