PALAEONTOLOGY head turtle which has been named by the writer Thallasochelys eoccenka ; while a fragment of the shell is sufficient to prove the existence at the same epoch of a species belonging to an extinct genus {Psephophorus) 'of leathery turtle.^ Vertebrae of two species of large serpents belonging to an extinct family also occur in the Bracklesham beds. One of these, Palaophis toliapicus, is typified by specimens from the London Clay of Sheppey ; but the second, P. typhceus, was described on the evidence of Bracklesham fossils. These snakes, judging from the form of the vertebra, appear to have been marine. The list of Bracklesham fishes is considerably larger than that of the reptiles, and includes at least nine species first described from that formation, some of which are peculiar to the same. First on the list come two species of saw-fish, Pristis cojitorttis and P. bisulcatus, the former of which is confined to the Bracklesham beds, while the latter also occurs at Barton, Hants. The flattened roller-like dental plates of eagle-rays are especially common in these deposits, and have been assigned to five species, namely Myliobatis dixoni, M. striatus, M. gonio- pkiirus, M. toliapicus, and M. latidens, the last alone being typified by Bracklesham specimens. There are likewise two species of ray belong- ing to the allied genus Aetobatis, of which A. ftiarginalis is exclusively from Bracklesham, while A. irregularis also occurs in other Eocene deposits, and is typically from the London Clay. Among sharks there are three representatives, Odontaspis elegans, O. macrota^ and O. cuspidata, of an extinct genus nearly related to the living porbeagle ; the three species are widely spread, and the first occurs at Newhaven as well as at Bracklesham Bay. There is also an extinct species of porbeagle, namely Lamna vince?iti, not peculiar to the Bracklesham beds, as well as the so-called Otodus obliquus, occurring elsewhere in the county in the Middle Eocene beds of Bognor. Large teeth from Bracklesham have been assigned to Carcharodon auriculatus, a widely-spread extinct relative of the largest of living sharks (C. rondeletii). Another Bracklesham shark is Galeocerdo latidens, a species likewise with a wide geographical distribution. Of fish allied to the living chimasra, or ' king of the herrings,' there are two representatives, Edaphodon bucklandi and £. leptognathus, both common to other Tertiary horizons. Fish-spines described as Coelorhynchus rectus are also found in the Bracklesham deposits, from which came the type specimens. Among the pycnodont ganoid fishes, in which the palate and lower jaw are armed with a pavement of spherical or oval crushing teeth, the species Pycnodus kcenigi was first described from Bracklesham, but has been subsequently identified from the corresponding formation of Belgium. As ' cat-fishes ' (Siluridc^) are comparatively rare as fossils, it is 1 Cat. Foss. Rept. Brit. Miis. iii. 224. 2 For the generic of this and two of the undermentioned species, see A. S. Woodward, Proc. Geol. Assoc, xvi. 10 ; in Cat. Foss. Fish. Brit. Mus. they are assigned to Lamna. 29
