150 



CHELONIA. 



Fig. 36. 



Thalassemys raetimeyeri. 



-The imperfect carapace ; from the Purbeck 

 of Swanage. -i. 



Genus ACICHELYS, Meyer 1 . 



Syn. Eury sternum, Wagler 2 . 

 Aplax, Meyer 3 . 

 Euryaspis, Wagner 4 . 

 Palceomedusa, Meyer 5 . 

 Achelonia, Meyer 6 . 



The type genus. Carapace flattened, distinctly emarginate an- 

 teriorly, with the costals well ossified and the posterior neurals not 

 forming a tectiform ridge on the carapace ; neurals long and more 

 or less distinctly hexagonal, with short antero-lateral surfaces ; 5th 

 neural with entire postero-lateral border. Vertebral shields very 

 wide, with the underlying areas more or less distinctly fluted. 

 Marginals long and narrow. 



1 Neues Jahrb. 1854, p. 579 ; the name does not occur in 1843, p. 585, as 

 often quoted. 



2 In Meyer's Palreologica, p. 103 (1832). Preoccupied by Eurystemus, 

 Dalman, Ephem. Entomol. p. 8 (1824). The name does not occur in ^Yagler's 

 Syst. Amplub. (1830). 3 Op. cit. 1843, p. 585.— Inappropriate. 



4 Abh. k.-bay. Ak. Wiss. vol. ix. pt. i. p. 89 (1861). 



•"> Fauna der Vorwelt— Kept. Lith. Schiefer, p. 136 (1860). u Ibid. p. 140. 



