186 CHELONIA. 



It cannot be proved that this genus (which is therefore provi- 

 sional) is really distinct from Hydropelta, Meyer 1 , of the Kimeridgian 

 Lithographic limestone ; or from Chitracephalus, Dollo 2 , from the 

 Wealden of Belgium. The latter genus is founded on immature 

 Chelonians, in which the skull is much elongated and has open 

 temporal fossse. The difference of this type of skull from that of 

 Idiochelys is, so far as it goes, in favour of the distinctness of 

 Hylceochelys from Chitracephalus. The genus Chelonides, to which 

 the present appears allied, is noticed under Plesiochelys. The 

 generic term Plastremys was never sufficiently defined, and is 

 practically a MS. name. 



Hylseochelys latiscutata (Owen 3 ). 



Syn. Pleurosternum latiscutatum, Owen 4 . 

 Platemys latiscutata, Maack 5 . 

 (?) Pleurosternum Jcoeneni, Grabbe 6 . 



The type species. Of comparatively small size, with the plastral 

 vacuity nearly obliterated. Neural bones very long, and in the 

 undermentioned specimens, at least, seven in number ; 3rd costals 

 frequently meeting in the middle line behind the 3rd neural. 

 Nuchal relatively short and wide, with moderate emargination. 



The type specimen is a carapace from the Purbeck, and is figured 

 by Owen in his ' Wealden and Purbeck Reptilia ' (Mon. Pal. Soc), 

 pt. i. pi. i. In that specimen the 3rd neural bone is in contact 

 with the 4th, and an 8th neural is represented as connecting the 

 7th with a suprapygal. The same features are shown in the 

 restoration of Pleurosternum Jcoeneni given by Grabbe in the 

 ' Zeitschr. deutsch. geol. Ges.' vol. xxxvi. p. 20 ; but from the 

 figure of the original specimen given in pi. i. of the same volume, 

 it is quite evident that the 8th costals met in the middle line, and 

 the same may have been the case with the type specimen. P. 

 Jcoeneni is from the German Wealden, and, so far as can be deter- 

 mined from the ventral surface of the carapace, belongs to the 

 present form. 



Hab. Europe (England and [?] Germany). 



1 Fauna der Vorwelt-Kept. Lith. Schiefer, p. 139 (I860). 



2 Bull. Mus. R. Hist. Nat. Belg. vol. iii. p. 70 (1884). 



ri Wealden and Purbeck Eeptilia (Mon. Pal. Soc), pt. i. p. 9 (1853).— 

 Pleurosternum. l Loc. a if. 



5 Palocontographica, vol. xviii. p. 295 (1869). 

 G Zeitschr. deutsch. geol. Ges. vol. xxxvi. p. 19 (1884). 



