J. Buckman, 1844. 
is 
racil 
sg 
mmonite 
A 
CEPHALOPODA Ammonites gracilis 
J. Buckman, 1844. 
Original description 
(1844. — Buckman, in Murchison, Geol. of Chelt., New Ed., pp. 71 and 104). 
[74] « Ammonites gracilis (Buckman), Tab. 3, f. 7. Sevenhampton Slate. Name proposed 
by Bernhardt Smith, Esq. 
[404] « À. gracilis (Bernhardt Smith). — Keel crenated, volutions 6 or 7, half concealed, 
ribs straight, passing over the back, and thus making the crenations of the keel; sometimes 
two or three ribs are confluent towards the front. Diameter about 9 in ; thickness 1 1/4 in.; 
aperture sagittate. 
« LOcaLITY. — Stonesfield Slate, Sevenhampton Common. » 
OBSERVATIONS 
The original description may be thus supplemented : The specimen is considerably 
crushed and therefore the proportions, especially those of the apertural view, are wholly 
incorrect. There is also, in consequence, no keel. The periphery would be rounded 
(somewhat convexi-fastigate), and the ribs would pass over the area without any diminution, 
apparently. The aperture would not be sagittate, but ovate, the width to the length being 
about as 7 to 10. 
As now preserved the specimen shews, in regard to ornament, in the umbilicus nume- 
rous small close-set costæ. These become later more distant. On the exposed whorl, the 
ribs on the inner area are somewhat stouter and more distant than those on the outer, each 
rib on the inner area giving rise, apparently, to two ribs on the outer area ; but condition of 
preservation has obscured these details. 
The dimensions given are incorrect : the specimen is $ 3/4 inches (146mm) across; the 
width of the aperture is actually 7/8 in. (22mm). The umbilicus is 46mm in diameter. Restored 
dimensions, if uncrushed, would be — aperture, length, about somm ; width, about 34mm, 
In details the suture-line, which is not very clearly shewn, agrees somewhat closely with 
that depicted by d'Orbigny for Am. Backeriæ (1846. — Pal. Fr. Ter. Jurassig., T. I, 
p- 424, PI. CXLVII, fig. 3) but it appears less ornate. The superior lateral lobe of 4. gracilis ïs 
shorter, broader, and less lobulate, the inner lobule being quite small. To fig. 1 on this plate 
of d'Orbigny’s, À. gracilis has a general resemblance ; but evidently differs by its much 
smaller umbilicus. 
Genus. When it has been mentioned in recent litterature, A. gracilis has been placed in the 
genus Perisphinctes, Waagen, a very heterogeneous series. Perhaps it may belong to 
Siemiradzkia Hyatt (Eastman-Zittel, Textbook Palaeont., Ceph., p. 582). 
Locality and Horizon. The locality, Sevenhampton Common, is 4 miles due east of Chel- 
tenham, Gloucestershire, and about 1 mile west of the village of Sevenhampton. The slaty 
beds of this locality are presumed to be on about the same horizon as the slate beds of 
Stonesfield in Oxfordshire. They form part of the Bathonian series, and are at present 
assigned to the zone of Macrocephalites Morrisi, Oppel. 
For the excellent photographs of this specimen my thanks are due to Mr. J. W. Tutcher, 
of Bristol. His careful work deserves the best acknowledgment. 
This specimen was refigured by Morris and Lycett (1854. — Great Ool. Moll., (Pal. 
Soc.) PI. xïii, fig. 2) 
1904. S. S. Buchman. 
38° 
