120 INFERIOR OOLITE AMMONITES. 



hard ironshot stone (Bed No. 3, in my section at Oborne, page 8) ; and in the 

 same zone at Wyke Quarry. It is one of the most distinctive fossils for that zone. 

 Besides these places, it has been obtained at quarries near Sherborne, and at 

 Louse Hill, in Dorset, and Milborne Wick, in Somerset. 



Dr. Haug 1 says that this species occurs in the Parkinsoni-zone of Normandy. 

 This is very interesting, being contrary to my experience of Dorset. I have found 

 no specimen in the ParMnsoni-zone, and probably not even in the upper part of the 

 Humphriesianum-zone at any locality. I have always considered it as a most 

 characteristic species for the Humphriesianum-zone proper, in which it is associated 

 with innumerable varieties of Stephanoceras Humphriesianum, with St. Braiken- 

 ridgii, Sphseroceras Gervillii, Sph. Brongniarti, Sph. Wrighti, &c. 



On account of the mistake in the explanation given by d'Orbigny for the plate 

 whereon he figured it, this species was formerly often quoted from Dorset under the 

 name Am. cadomensis until I corrected the error in my paper on Inferior-Oolite 

 Ammonites. 2 



Plate XXII, fig. 1, shows the side view of a specimen with the mouth-border from 

 Oborne (third bed of the Section on p. 8) ; and fig. 2 gives the back view. Figs. 

 3, 4, illustrate another example from Sherborne. Figs. 5, 6, illustrate a singular 

 variety, with the small umbilicus which is usually peculiar to the inflated forms. 

 This specimen is from Wyke Quarry (second bed of Section, p. 8). Figs. 7, 8, give 

 a smaller example from Sherborne. Figs. 9, 10, mark a specimen with numerous, 

 but unequal, ribs ; it is from Sherborne. Fig. 11 shows the side view of a specimen 

 with only finely marked lines of growth on its body-chamber ; it has the mouth- 

 border, and came from Oborne. In fig. 12 is given the back view, showing 

 unusually rudimentary furrows. The side view of a thick globose form, with the 

 mouth-border, is exhibited in fig. 13 ; and a view of this mouth-border, with its 

 ventral process and ventral furrows continued thereon, is shown in fig. 14. This 

 specimen came from Oborne. In figs. 15 and 16 is depicted another thick example, 

 which is also from that peculiar thin development of the Humphriesianum-zone at 

 Wyke Quarry. Figs. 17 and 18 are the side and back views of a specimen from 

 Sherborne. Its ribs are somewhat irregular in size. The young specimen 

 delineated in figs. 19 and 20 is very interesting, and shows what is the juvenile 

 stage of the globose forms (figs. 13 — 16). The specimen of course shows propor- 

 tionately more umbilicus than they do, and also whorls more inflated ; but this is 

 exactly what is found in all other species. This specimen again is from Wyke 

 Quarry. In figs. 21 and 22 are given views of a very umbilicate variety. This 

 variety is scarce, and seems never to have attained a large size ; but here it is 

 sufficiently large to show that it could not possibly be the young of any of the 



1 Op. cit., p. 639. 



2 ' Quart. Journ. Geol. Soc.,' vol. xxxvii, 1881, p. 604. 



