38 UPPER CRETACEOUS TELEOSTS 
Hototyre. B.M.N.H. specimen number 4039, an imperfect left ectopterygoid 
from the Chalk of Sussex. 
MATERIAL. Specimens in the B.M.N.H., notably numbers P.1810a and P.1811. 
The latter specimen was figured by Woodward (1902 : 45, pl. 12, fig. 1), and both 
specimens were prepared in acetic acid. The holotype of Gtinther’s (1864) Plintho- 
phorus robustus, number 38113 in the B.M.N.H. (figured by Woodward, 1902, pl. 12), 
was also examined and is placed in this species as Woodward (1go1 : 229) tentatively 
proposed. 
ReMARKS. Leidy’s naming of Cimolichthys levesiensis on palatine and ecto- 
pterygoid material was the first recognizable description of the species after Agassiz’s 
errors in ascribing these to the genus Saurodon. Between these two references 
Reuss (1845) had described isolated teeth of a cimolichthyid as the fin spines of a 
shark. Leriche (1902) synonymized the two species under the name Cimolichthys 
marginatus (Reuss). However Leriche was definitely using Cimolichthys levesiensis 
material, whereas the earlier material used by Reuss was not so definitely attribut- 
able to this species. 
The following are the references to Cimolichthys marginatus 
1845 Spinax marginatus Reuss : 8, pl. 4, figs. 10, 11. 
1848 Acanthias marginatus (Reuss) Giebel : 301. 
1855 Anenchelum marginatum (Reuss) Hébert : 350, pl. 27, fig. 4. 
1874 Anenchelum marginatum (Reuss) ; Barrois : 131. 
1874 Trichiurides (Anenchelum) marginatum (Reuss) Winkler : 39. 
1875 Saurocephalus marginatus (Reuss) Geinitz : 226, pl. 43, fig. 38. 
1887 Saurodon marginatus (Reuss) Dames : 77. 
1897 Saurocephalus marginatus (Reuss) ; Leonhard : 69, pl. 6, fig. 17. 
DESCRIPTION. Neuvocranium. The neurocranium is shown in dorsal, ventral, 
lateral and posterior views in Text-figures 16 to 19g. _ It is long and shallow with the 
maximum width occurring behind the orbits. The snout is very acutely pointed 
but the neurocranium gradually becomes wider more posteriorly. 
The frontals form practically the whole of the skull-roof and are long tapering 
bones ending anteriorly by insertion on to the rear edges of the mesethmoid. Each 
frontal meets its fellow in the mid-line in a straight suture and overlaps the parietal 
and supraoccipital posteriorly. Postero-laterally the frontal is excavated above the 
sphenotic and the pterotic and only enters slightly into the roof of the post-temporal 
fossa. The surface ornamentation of the frontal is confined to the more lateral 
regions and is in the form of ridges of bone radiating from the centre of ossification 
above the sphenotic. The ridges which extend anteriorly terminate on the lateral 
edge of the frontal anterior to the orbit, those ridges which extend antero-laterally 
terminate on the edge of the frontal where it forms the upper border of the orbit. 
The ridges which extend posteriorly are arranged in a fan, each ridge ending on the 
edge of the frontal where it overlaps the other roofing bones posteriorly. 
The supraoccipital extends on to the skull-roof and forms part of the hind wall of 
the neurocranium. Anteriorly the supraoccipital is overlapped by the frontals and 
