228 DESCRIPTIONS OF THE BOGNOR FOSSILS. 
Pseudoliva semicostata. (Tab. XIV. fig. 26.) 
The French shell is smaller and apparently more regularly ribbed, but there 
can be little doubt of the species being the same, although I have not been able 
to compare specimens. 
MOLLUSCA CEPHALOPODA. 
TETRABRANCHIATA. 
Nautilus. 
Four species of this genus, found at Bracklesham and Bognor, may be distin- 
guished by the following marks :— 
Nautilus imperialis. 
Orbicular, slightly flattened ; umbilicus open ; septa twice curved, their sides 
broad ; front rounded ; siphuncle nearly central. 
Nautilus Sowerbii. 
Lenticular ; umbilicus open; septa twice and very much curved, their sides 
narrow ; front angular; siphuncle near the inner edge of the septum. 
Nautilus centralis. 
Globose ; umbilicus open ; septa once curved, the side lobes broad ; siphuncle 
central. 
Nautilus regalis. 
Oblate spheroidal ; umbilicus filled up; septa once curved; front obtuse or 
flattened ; siphuncle nearly central. 
Nautilus urbanus, found in London and at Sheppey, is like N. regalis, but 
flatter, and has the siphuncle near the inner edge of the septum: it probably 
belongs to a higher bed than the Bracklesham or Bognor beds. 
PISCES. 
Otodus obliquus. (Tab. XV. fig. 11.) 
This species, determined by M. Agassiz, is very common at Sheppey. 
Teeth and vertebrz of fishes, so common at Bracklesham, are very seldom met 
with at Bognor. 
