CEPHALOPODA Ammonites Colesi 
J. Buckman, 1844. 
Original description 
(1844. — Op. cit., pp. 103 and 89). 
« A. Colesi, Tab. 12, f. 2. — Keel very sharp without furrows, volutions $ or 6; 
one-third concealed, ribs simple, somewhat curved forwards, rather distant, whorl gradually 
diminishing. Diameter about 3 1/2 in., thickness 3/4 in. 
« Locazrry. — Lias Shales, Railway cutting between Cheltenbam and Gloucester. Very rare. 
Named in honor of H. Coles, Esq., surgeon, of Cheltenham, who, whilst engaged in the 
practice of an arduous profession, is not unmindful how much the mind may be enlarged 
by the study of nature. » 
[P. 89.] « L. S. Raïlway cutting, near Swindon, Gloucestershire. » 
OBSERVATIONS 
The type of the species was described afresh by S. S. Buckman (1894. — Geol. Mag., 
Dec. IV, vol. I, no 362, p. 361) under the title Agassiceras Colesi, in the following terms : 
« Discoidal, much compressed, strongly carinate. Whorls in youth evidently gibbous, rather 
strongly and widely costate, gradually becoming flatter-sided, and ornamented with direct, 
slightly inclining costæ, which have a strong forward projection on the periphery, where 
they are very obscure. The costæ which are slighlty swollen at the edge of the inner 
margin, and again a little more swollen at the bend on the outer area, become practically 
obsolete towards the end of the whorl (specimen 8gmm in diameter). Periphery fastigate, 
divided by a strong carina. Inner margin well defined on last whorl, upright. Inclusion 
one-third. » 
To this may be added, that the keel is presumably hollow, that the early whorls, to about 
8mm diameter, are smooth, representing the Am. lævigatus stage, that the next whorl is 
strongly costate, representing a stage like Am. halecis, that the later whorls approach the 
Oxynotoceratan character, only that the umbilicus is large. There is more than halfa-whorl 
body-chamber ; the last suture-line but one is marked. The septa are not distinctly shown, 
but they indicate the Asteroceratan pattern — a simple superior and inferior lateral lobe with 
a deep superior lateral saddle between. 
The generic position of this species may be thus stated : — it is cognate with Am. Scipio- 
nianus, d'Orb., which Hyatt placed in his genus Agassiceras ; but later he made it the type 
of his genus Æfomocerus. 
The horizon and locality recorded above may be thus interpreted : — Lower Lias (Upper 
Sinemurian, zone of Am. oxynotus with Am. cultellus [pars = oxynotus] and Am. accipitris) 
cutting on the Midland Railway at Swindon, 2 miles N. W. of Cheltenham, Gloucestershire. 
The species is extremly rare. 
1904. S. S. Buchman. 
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