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CEPHALOPODA Ammonites sulcatus 
J. Buckman, 1844. 
Original description 
(1844. — J. Buckman, in Murchison, Geol. of Chelt., New Ed., pp. 105-106 and 91). 
[405] « 4. sulcatus, Tab. 11. f. 1, 2, and 3. — Back with a deep furrow in young 
specimens, which becomes obliterated in older ones; whorls 3 to 4, mostly exposed ; ribs 
close and fine in the young state, stronger and more distant in older specimens, alternately 
long and short, sometimes anastomosing and either breaking off at the furrow, or running 
straight across the then square back, [106] according to the age of the specimens ; aperture 
oblong, diameter 1 inch; thickness 3 lines. 
« Locazrry. — Lias Shales, Vale of Gloucester, principally from the Raïlway cuttings. This 
shell is much like the 4. lacunatus, but may readily be distinguished by its stronger ribs, 
and the obliteration of its furrow in the older states, whereas, in the lacunatus, it is keeled in 
the young state. The À. lacunatus, and sulcatus (Buckman), and acuticosta (Strickland), offer 
rare exceptions to the Lias Ammonites, in being furrowed at the back, that being a character 
more frequently appertainine to Ammonites of the Gault and Green-sand formations. » 
[91] « Ammonites sulcatus(Buckman).Tab.11.f.1,2,and 3. L.S. Nearthe Cheltenham Station. » 
OBSERVATIONS 
Three specimens were figured as Am. sulcatus, and the figures shew three different forms : 
1, fine-ribbed ; 2, coarser ribbed with interrupted periphery ; 3, coarser ribbed without 
interrupted periphery. The specimens, which are now reproduced, may be described as follows : 
Fig. 1 (T.1). Inflated, with nearly circular aperture, fine-ribbed ; vibs cross periphery on 
most of exposed whorl, there is only slight interruption near the last part ; whorls about 
half concealed ; specimen wholly septate. 
Fig. 2 (T2). Compressed, aperture quadrate, ribs coarse, somewhat approximate, 
somewhat flexed, slightly swollen around umbilicus where they are joined in pairs, also 
slightly swollen at edge of periphery, where there is an interruption — the break becomes less 
distinct towards end of whorl. About 1/4 whorl seems to be body-chamber. 
Fig. 3 (T3). More evolute than T.? ; shape of aperture a truncate triangle ; whorls 
inflated around umbilicus ; costæ coarser than in T.? and more distant, heavy around umbi- 
licus, where they are almost nodose, thence the ribs divide, they are somewhat flexed, and 
irregular. Periphery flat, crossed by strong costæ, only a sign of interruption towards end of 
whorl. About 1/2 a whorl seems to be body-chamber. 
T.? being the most « sulcate » of the series should be selected as the holotype. T.! and 
T3 differ from it, and from any similar forms figured by Sowerby, Wähner, Canavari, and 
others. T.! resembles À. lacunatus rotundus, Quenstedt, but is more coarsely costate, and 
bardly shews peripheral interruption, much less sulcation. This feature distinguishes it from 
A. lacunoïdes, Quen., and also from A. ventricosus, Sow., as interpreted by Canavari and 
Wähner. It may be named subrotundus. T3 differs from À. catenatus, Sow., as interpreted by 
Canavari, by its larger umbilicus, around which are nodose ribs, by the ribs more flexed and 
irregular, and by their being much stronger on the periphery — Canavarÿs interpretation is 
accepted as Sowerby’s figure in De la Bèche (1833. — Geol. Manual, p. 333), is insufficient. 
The form now figured may be named jugatus, on account of the strong ribs crossing the 
periphery, a character which separates it from Æpgoceras (Schlotheimia) postaurinum, Wähner. 
Locality and Horizon. — The records may be taken to shew that the specimens were 
obtained from the Lower Lias near Cheltenham during the making of the Bristol and 
Birmingham Railway. The mineral characters of the specimens suggest that they came from 
the same bed as the Arnioceras Bodleyi figured ‘Pal. Univ. PI. XXXVI. This would explain 
a record sometimes given in English works of «4m. angulatus being found with A4». 
semicostatus, sulcatus-like forms having been mistaken for angulatus. Then it may be 
suggested that the record for sulcatus and allies should be Lower Lias, Sinemurian, zone of 
<Arnioceras semicostatum, neighbourhood of Cheltenham, in same bed with 4. Bodleyi. 
Genus.— Schlotheimia, vide Hyatt, Canavari, Wähner in regard to species quoted in comparison. 
Note. — In the present series there may be seen the whole course of development from 
non-interrupted periphery (Waæhneroceratan) to interrupted (Schlotheïmian) and commencement 
of return to non-interrupted (gerontic decline). But T.$ is not an older form of T.? as my 
father seemed to think (p. 106) : it is biologically a younger species, retaining the 
Wæhneroceratan character of periphery. 
Summary. Am. sulcatus J. Buckman, fig. 1, 2, 3. — 1. Schlotheïmia subrotunda, sp. nov; 
2. = Schl. sulcata (J. Buckman); 3. — Schl. jugata, sp. n. 
My best thanks are due to Mr. J. W. Tutcher for the photographs. 
1904. S. S. Buchman. 
39° 
