CEPHALOPODA Ammonites lacunatus 
J. Buckman, 1844. 
Original description 
(1844. — Buckman, in Murchison, Geol. of Chelt., New. Ed., p. 105, p. 90). 
[405] « A[mmonites] lacunatus, Tab. 11. f. 4 and 5. — Back with a single furrow, which is 
very narrow ; volutions 4 or 5, flattened, half concealed ; ribs fine, close, alternately long 
and short, sometimes anastomosing ; the dorsal furrow is wanting in young specimens, 
when the ribs unite at the back with a slight angle. Aperture small, oblong, diameter about 
1 1/2 in., thickness 3 lines. Rare. 
« are — Lias Shales ; from a nodule of Lias found in a brook at the foot of Dowdeswell Hill. 
[90] « A[mmonites] lacunatus (Buckman). Tab. 11. fig. 4 and 5. L. S. Railway Cuttings, 
vale of Gloncester. » 
OBSERVATIONS 
Neither of the co-types can be found. There are 6 specimens in a box inscribed 
« À. lacunatus, Buck., Lias, Cheltenham, » by my father. So these are metatypes. Of these 
specimens, M!, M?, Mi, are evidently from clay beds, while the others are from a hard stone 
bed, presumably the nodule mentioned : that is also in my possession. 
These 6 specimens all agree in being more or less finely costate. But among them are 
five distinct forms : M!, finelv costate and evolute ; M?, costæ rather stronger, evolution not 
so much ; M3, costæ still stronger, evolution again less, while the w Horls are stouter ; 
Mi, Mi, involution greater than M5 and whorls more compressed : M6, quite distinct because 
of the obliteration of its ribbing. 
Of these forms M! agrees best both with fig. 4, which represents the umbilicus much 
exposed and the boris. but little occluded, and with the description, shewing more than 
the other forms « the ribs fine, close, alternately long and short ». It differs in regard to 
the phrase « volutions half concealed » which again “does not agree with the figure. But 
while the other specimens shew that forms with volutions half concealed were regarded as 
belonging to the species; vet this very phrase may have been applied to a form like Mt itself. 
For if it be held in the ordinary manner between the observer and the light (especially with 
artificial light) so that the shadow of the outer whorl falls into the biens there is 
just the appearance of « volutions half concealed ». More than one person into w hose hands 
I have placed this specimen for an opinion, has been deceived by this matter of lighting into 
saying « whorls half-covered ». Therefore the discrepancy between the description and the 
figure is not so great as would be supposed ; it is a mistake very easily made. 
The statement that « the dorsal furrow is wanting in young specimens » [ cannot confirm ; 
but if such is the case, it is the Wæhneroceratan stage (vide 4. sulcatus, Pal. U., 39). 
Genus. — Schlotheimia Bayle, vide Canavari, Hyatt, Gever, etc., in reference to similar forms. 
Locality, — « The Gloucestershire specimens were collected out of the Lower Lias Shales 
and Limestone near the Midland Raïlway-cutting at Lansdown New Road [Cheltenham], about 
the horizon of Amaltheus oxynotus » W right (1882.— Palaeont. Soc. Monogr. Lias Amm., p. 331). 
The statement in the original description about thenodule « found in a brook at the foot of Dow- 
deswell Hill » must be incorrect, unless it had been taken there by human agency. Dowdeswell 
Hillis to the east of Cheltenham, at a much higher level actuaily and geologically, the strata 
are of striatus-zone or above. Besides À. Fowleri (Pal. U. , 37) came from a stone similar to 
that of the nodules : and that species was obtained at Lansdown Station, Cheltenham. 
Concerning the other specimens :—M? appears to be similar to Am. Tacunatus Dumortier 
(1867. — Dépôts Juras. Rhône, II, PI. XXI, fig. 18-20) andto 4ev. lacunatum Wright (Op. cit., 
PI. DVI. fig. 16-18). Dumortiers form is regarded by Canavari as a synonym ot his Aegoceras 
ee (1882. — Fauna des unteren Lias von Spezia. Palacontographica, T. XXIX, Liefer. III, 
p. 166, Taf. XVII, fig. 3, XIX, fig. 1). So M? may be inscribed Schlotheimia deleta ? M3 may 
be À. lacunoides Quenstedt (Am. Schuæb. Jura, PI. XXI, fig. 24). Miis new : it is too thin for 
chloth. Geyeri Hyatt, too coarsely ribbed for S. angustisulcala Gey er. It may be called S. parva. 
M is a young example of this species. Mis quite distinct : it may becalled Schlotheimia subpolita. 
Mi, Mi, M6 occur in the limestone band with 4. Fowleri (Pal. U., 37). M!, M2, M occur 
in clay ; but whether just above or just below is not yet known. 
For the photographs of these spécimens my best thanks are due to Mr. J. W. Tutcher, 
who, with his usual kindness, has taken great trouble to secure such good pictures. 
Summary : M! Schlotheimia lacunata (]. Buckman). 
M? » deleta (Craer) ? 
M3 » lacunoïdes (Quenstedt) ? 
Mi, M » parva sp. nov. 
M5 » subpolita sp. nov. 
Locality. Cheltenham ; Horizon, Sinemurian (Lower Lias); Hemeræ, stellaris-oxynoti. 
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1905 S. S. Buchman. 
PALAEONTOLOGIA UNIVERSALIS. — 78" 
