115 
A 
AMMONITES striatus. 
TAB. LIII. — Fig. 1. 
Spec. Char. Disceid, gibbose, inner whorls con- 
cealed, obscurely undulated,, finely striated lon- 
gitudinally; septa rather distant., with four 
large angular folds/ 
Thickness rather more than half the diameter; striae 
extremely numerous and very regular, the aperture is 
semicircular with nearly parallel edges; siphunculus at 
the outer margin of the septum, where it is slightly 
notched. The shell is very thin. 
This resembles the species in Sir Edward Hulse’s collec- 
tion, that was Lethieulier’s, and is figured in three views in 
Tab. 19 of his M.S. in that Gentleman’s valuable Library, 
it is said to be found in Pools-hole in the Peak, Derbyshire. 
It seems to be the less globular variety mentioned by 
Mr. Martin in his description of Nautilus sphaericus, our 
next figure. I suppose our specimen to be from near 
Buxton or Castleton in Derbyshire. I believe the shelly 
remains are very seldom so perfect as in this specimen; and 
it is somewhat convenient that they did not quite cover it, as 
the zigzag septa would then have been entirely hid. The 
shell must have been beautifully delicate when in a recent 
state, as the elegant transverse undulations pass in very fine 
semicircular curvatures, with the sharp ends meeting in 
points upwards (dnly to be seen with a magnifier), passing 
into straighter lines by degrees to the sides. The zigzag 
separations are very distinct without passing into the 
foliated sutures that characterize most of the Ammonites, 
