NATICA. 
269 
Section B. — Mammillated. 
203. Natica cf. Michelini, d'Archiac, 1843. Plate XX, figs. 18 «, 18 b. 
1843. Natica Michelini, d’Archiac. Mem. Soc. Geol. France, vol. v, 2nd part, 
p. 377, pi. XXX, fig. 1. 
1851. — — — Morris and Lycett, Great Ool. Moll., part i, 
p. 44, pi. vi, fig. 3 (non fig. 2). 
1852. — — — D’Orbigny, Terr. Jur., ii, p. 192, pi. 
cclxxxix, figs. 11, 12. 
1884. Ampullina Michelini, d’Archiac. Cossmann, Ft. Bath., p. 131, pi. ii, 
figs. 9, 10. 
Bibliography, ^c. — D’Archiac’ s diagnosis is repeated by d’Orbigny. The shell 
is described as thick, ovoid, and with a very sharp spire, apex mammillated ; seven 
whorls, the last very enveloping, and depressed near the suture, 
Morris and Lycett described what they regarded as two varieties. Of these 
the longer and commoner form has only a faint degree of resemblance to 
d’Archiac’ s figure. Hence de Loriol {fide Cossmann, loc. cit.) has renamed this 
form Natica Minchinhamptonensis (‘ Alpes Vaud.,’ p. 13, pi. i, figs. 8, 9), 
The Inferior Oolite variety to which I now call attention has much more 
resemblance to d’Archiac’ s species than the Minchinhampton shell renamed by 
de Loriol, but it presents also considerable differences. 
Description of Inferior Oolite Variety : 
Spiral angle .... 106°. 
Height of body- whorl to entire length . . 85 : 100. 
Length of figured specimen . . .31 mm. 
The points wherein this form differs materially from Natica Michelini are — it is 
narrower, the shoulder is less sloping, and the body-whorl is less globose. There 
are other differences such as absence of callus on the inner lip, &c., which may 
possibly be due to conditions of preservation. There is no visible umbilicus. 
Relations and Distribution. — This form almost stands alone in the Inferior 
Oolite. The very effuse aperture also serves to distinguish it from all other species 
except Natica cincta. In the Northampton Sand are casts of a very large Natica, 
which is closely related, possibly identical. A few specimens are known from the 
Oolite Marl of the Stroud-Nailsworth district ; and there is a specimen, 45 mm. 
long, in Mr. Walford’s collection from the Gryphite-grit of Bourton-on-the-Water 
which might be assigned to this variety of Natica Michelini. 
There are some very small specimens from the Oolite Marl which might be 
regarded as micromorphs of Natica Verneuili, d’Arch., or of some closely-related 
species. These I have not ventured to figure. 
