368 SCAPHITE. 
were partly internal, and partly external shells ; 
where the spines are present, the portion so armed 
was probably external. Nine species of Hamites 
occur in the single formation of Gault or Speeton 
clay immediately below the chalk, near Scar- 
borough. (See Phillips' Geology of Yorkshire.) 
Some of the larger species equal a man's wrist 
in diameter.* 
Scaphite. 
.M. 
The Scaphites constitute a genus of Elliptical 
chambered shells, (see PI. 44, Fig. 15, 16,) of 
remarkable beauty, which are almost peculiar 
to the Chalk formation ; they are so rolled up at 
each extremity, whilst their central part continues 
nearly in a horizontal plane, as to resemble the 
ancient form of a boat ; whence the name of 
Scaphite has been applied to them.^ 
* The Hamites grandis, (Sowerby, M. C. 593,) from the Green 
sand at Hythe, is of these large dimensions. 
t The inner extremity of the Scaphite is coiled up like that of 
an Ammonite, (PI. 44, Fig. 15, c. and Fig. 16) in whorls embracing 
one another ; the last and outer chamber (a) is larger than all 
the rest together, and is sometimes (probably in the adult state) 
folded back so as to touch the spire, and thereby materially to 
contract the mouth, which is narrower than the last or outer 
chamber. (PI. 44, Fig. 15, b.) In this character of the external 
chamber, the Scaphite differs from the Ammonite ; in all other 
respects it essentially agrees with it ; its transverse plates being 
numerous, and pierced by a marginal Siphuncle, at the back of 
the shell (Fig. 16, a.); and their edges being lobated, deeply cut, 
and foliated. (Fig. 15, c.) 
