Ammonites. 
CEPHALOPODA. 
245 
Discoidal, with six or seven volutions, two-thirds exposed, 
smooth; transversely ribbed, alternately two short, reaching 
half across the volution, and one long, emanating from the 
dorsal margin, the longer ones becoming thickened towards 
the inner margin; shorter ones curved backwards, near the 
dorsal edge; ambit or back rounded, with a slight depression 
in the middle, formed by the ribs, which nearly meet; aperture 
terminating on each side with a spatulate projection of about 
one and a half inch in length, and three-eighths in width. 
In the Oxford Clay, Christian Malford. 
10 . Ammonites Elizabeths.— Elizabeths Ammonite, pi. 
XX.** figs. 1, 2, 3. 
A. Elizabeths. Pratt, Ann. Nat. Hist. VIII. p. 162, pi. 3, 
figs. 1—4. 
Volutions six or seven, about two-thirds exposed; angular, 
arising from a series of spines on each dorsal edge, and two 
rows of tubercles on the sides of the volutions, one near the 
middle, another smaller and compressed, near the inner mar¬ 
gin ; sides with transverse ribs, varying much in elevation, 
curvatures, and number; in some they are nearly straight, in 
others curved, and in another variety undulating, but generally 
becoming angular near the aperture in the adult shell; some 
form loops on the surface; aperture provided with a lengthened 
spatulate projection, its surface deeply marked by lines of 
growth; back narrow, concave, the ribs passing over it; 
siphuncle not visible. 
The great difference in those figured certainly would lead 
to the supposition that they are specifically distinct. I yield, 
however, to the opinion of Mr. Pratt, who has had an oppor¬ 
tunity of examining more varieties than J have done, fie 
says, that their characters “appear to indicate several distinct 
species, but on close examination, it is seen that all the 
varieties pass into each other, the same specimen sometimes 
containing more than one form.” 
The spines and rays (ribs) vary from sixteen to upwards of 
sixty on the last volution, and they are large and elongated in 
proportion to the smallness of their number. 
The Oxford Cla y, Christian Malford. 
11. Ammonites Stutchburii. —Stutchbury’s Ammonites. 
A. Stutchburii. Pratt, Ann. Nat. Ilist.VIII.p. 163,pi. 4, f. 1,2. 
Discoidal, with four two-thirds exposed volutions; sides with 
a series of short, distant, curved ribs, emanating from the inner 
sides of the volutions, terminating in compressed tubercles; 
beyond these, to the outer margin, are very numerous close-set 
waved ribs ; back narrowed, with the smaller ribs passing over 
it, and with a series of sharp serrated projections on both sides; 
aperture with a projecting beak. 
The Oxford Clay, Christian Malford. 
12. Ammonites flcctuosus. —The Fluctuating Ammonites, 
pi. XX.** fig. 16. 
A. Jluctuosus. Pratt, Ann. Nat. Hist. VIII. p. 164, pi. 6, 
figs. 1, 2. 
Discoidal or lenticular, surface smooth, with six two-thirds 
exposed volutions; crossed by thick, distant ribs, which, with 
a few exceptions, are forked for nearly their outer half; back 
plain. 
In the young condition there are numerous sharp, alternately 
long and short, ribs, the short ones combining in twos or threes 
with the longer ones about the middle of the sides, some 
remaining distinct. 
The Oxford Clay, Christian Malford. 
13. Ammonites Sedgwickii. —Sedgwick’s Ammonite. 
A. Sedgwicldi. Pratt, Ann. Nat. Hist. VIII. p. 163, pi. 5, 
fig. i. 
Discoidal, smooth, with five one-fourth exposed volutions, 
with a row of distant tubercles on the inner side, situated a 
little way from the margin; outer sides with numerous flat, 
close-set ribs, which do not reach half way across the volutions. 
The Oxford Clay, Christian Malford. 
14. Ammonites Brightii. —Bright’s Ammonite, pi. XX.** 
figs. 4 and 10. 
A. Brightii. Pratt, Ann. Nat, Hist. VIII. p. 164, pi. 6, 
figs. 3, 4. 
Discoidal, nearly smooth, with about seven two-thirds exposed 
volutions; with several flat, obtuse ribs emanating from the 
dorsal edge, which combine a little beyond the middle of the 
volutions into compressed, elongated tubercles, which reach 
the inner margin; the tubercles being about one-third as 
numerous as the ribs, and meet them in a rounded right angle; 
the siphuncle is distinguished by a sharp ridge on the back. 
The Oxford Clay, Christian Malford. 
15 . AmmonitesLonsdalii.— Lonsdal’sAmmonite, pi. XX.** 
% is. 
A. Lonsdalii. Pratt, Ann. Nat, Hist. VIII. p. 164, pi. 5, f. 2. 
Discoidal, three or four one-third exposed volutions, the last 
being more than half the diameter of the shell: surface with 
numerous transverse waved ribs, which emanate from the back, 
and hardly reach the middle of the volutions, become fewer and 
more obtuse as the shell increases in size, and pass into line 
stria3 near the aperture, which forms a regular concave termi¬ 
nation, except on the inner edge, where it bends back, some¬ 
what like the handle of a sickle. 
The Oxford Clay, Christian Malford. 
16. Ammonites sulcatus.— Tbe Furrowed Ammonites, pi. 
XX.** figs. 5, 6, 11,12. 
A. sulcatus. Strickland, Geo. Chelt. p. 105, pi. 11, figs. 1, 
2 , 3 . 
Moderately convex, with three or four volutions, almost 
wholly exposed ; crossed by alternately long and short curved 
strong ribs, increasing in thickness from the inner to the outer 
side; back with a deep furrow in the young state, which 
becomes obliterated when old ; when young, the ribs are fine 
and close ; back square in the adult; aperture oblong. 
The Lias Shales, Vale of Gloucester. 
3 c 
