258 
INFERIOR OOLITE AMMONITES. 
differs in having extremely fine ornamentation and a rather larger umbilicus. The 
other specimen (figs. 7, 8) has, up to the last half-whorl, a smaller umbilicus than 
Wright's ; and then it increases the size of the umbilicus suddenly. The termina- 
tion of this specimen was depicted PI. XXX, fig. 19 ; but I have found it necessary 
to have the complete specimen drawn as a type of the small-centred (until com- 
mencement of body-chamber) Cotteswold form. The distant ribs of the inner 
whorls — the signs of a Levesquei-stage — are to be noticed ; and also how quickly 
they give place to the fine strise. 
The specimen depicted in PI. XXX, figs. 15 — 17, is an example of the fine- 
ribbed south-country form, and may be recognised as the young of the specimen 
delineated PL XLIV, figs. 4—6. 
Dumortieria Moorei occurs in the same bed as Gramm. mactra. In the Cottes- 
wolds it characterises the lower part — the Moorei-heds — of the Opalinum-zone, 
though it is not so common a species as was at one time supposed. In the Dorset- 
Somerset district, where it occurs in the upper part of the Yeovil Sands, it is 
decidedly scarce. 
The species does not seem to be altogether widely distributed on the Conti- 
nent ; but then it has very possibly been confounded with other species besides 
Gramm. mactra. Branco, calling it " mactra,^'' states that it is " rather scarce in the 
upper part of the Trig .-navis-hedi^, Signalberg bei Boevingen ; " I have specimens 
from Gundershofen sent me by Dr. Haug ; and Quenstedt figures it from Swabia. 
Most interesting of all is its occurrence in Chili, South America ; as it is figured 
by Bayle and Coquand from Jorquera with Am. (Sonninia) pmtulifer^^ Ostreoj 
cymbium, and Spirifer tumidus.^ 
Figs. 4, 5 of PL XLIV give two views of the south-country variety of this 
species ; and fig. 6 is the suture-line from the same specimen. Figs. 7, 8 show j 
two views of a Cotteswold form of the species, with the completed end to the j 
body-chamber. This specimen came from Buckholt Wood, near Stroud, Grlouces- j 
tershire. Fig. 9 is the suture-line taken, with the kind assistance of Mr. B. T. j 
Newton, F.G.S., from the specimen contained in the Jermyn-Street Museum. 
In PL XXX, by figs. 15, 16, a nice specimen of the young form of the species 
is shown, in comparison with various examples of Gramm. mactra; and fig. 17 | 
is its suture-line comparable with fig. 7. This specimen came from the Yeovil 
Sands, Bradford Abbas, Dorset. In the same plate, fig. 19 is a portion of the 
specimen depicted in full in PL XLIV, figs. 7, 8. 
' See synonyms. 
2 One of the Sonninice from the Concavmn-hed of Dorset can be identified, I think, with Sonn, 
pustuUfera. 
