CHELONIA. 61 



border, and in the prominence of the connate extremity of the rib on its under surface, 

 is so great, as must impress the value of such characters upon the palaeontologist. 

 The outer surface of the present fragment presents a well-marked reticulate, or rather 

 pustular, pattern, but a coarser one than in the Tri. circumsidcafus. The reticulation 

 is continued to the beginning of the bevelled border in fig. 7, which slopes gradually 

 to an edge ; beneath which the free end of the rib projects. The Tri. rivosus most 

 resembles the present fragment in this character. 



The fragment is from Sheppy. I strongly suspect it to belong to a species distinct 

 from any of those from Hordwell ; and, in the hope of acquiring more illustrative 

 specimens, the attention of collectors is directed to it by the specific name and the 

 figure here given. 



Trionyx. -S^. ind. Bracklesham. 



The left hyposternal bone of the Tnomjjc from Bracklesham (figured in Tab. XIXZ), 

 fig. 7) resembles that from the Hordwell Eocene, referred to Trionyx planus (fig. ^,ps), 

 in the convexity of the inner border at that part where it is concave in the Tri. in- 

 crassatus (T. XIX, fig. ^, ps) \ but it differs from the Tri. planus in being uniformly 

 convex as far as the xiphisternal notch, and is not indented before forming that notch, 

 as it is in the Tri. planus (T. XIXZ)). The present hyposternal shows also very plainly 

 the base of a fractured tooth-like process of the subjacent hgemapophysis projecting from 

 the inner border, where there is no such trace of a process in the Tri. planus. There 

 are also the bases of a tooth-like process on both sides of the xiphisternal notch, and at 

 the posterior outer angle of the hyposternal bone. The external border of the bone 

 in advance of these processes is longer and straighter than in the corresponding part 

 of the hyposternal of the Tri. incrassafus. 



The species of Trionyx from Bracklesham cannot, however, be safely defined until 

 the characters of its carapace are known. The present specimen forms part of the 

 valuable and instructive collection of Frederick Dixon, Esq., F.G.S. 



Family — Paludinosa. 



This family, if regard were had to the number of species it contains, might be 

 deemed the typical one of the order Chelonia. But in the series of extinct species, from 

 the particular formation of Great Britain, to which the present Monograph is restricted, 

 the number of marsh tortoises is small in comparison with those that were more truly 

 aquatic {Fluvialia), and which inhabited the sea {Marinci) ; and such a result might 

 have been anticipated from the nature of their matrix, as it is elucidated by other 

 classes of fossil animals, the remains of which are found in the London clay. 



The feet of the Paludinosa have the digits comparatively free ; more than three 



