S. S. Buckman—On Jurassic Ammonites. 203 
Non Ludwigia corrugata, Douvillé. 
When young, this species possesses coarse ribs, more or less joined 
towards the inner margin, and projected forwards on the ventral area ; 
it has a small keel sunk between two furrows; and the preceding 
whorl is covered about one-half by the next. It soon loses its fur- 
rows, obtains a large hollow carina, and at a later date loses its ribs; 
its envelopment is now two-thirds, quickly decreasing again to one- 
half at the mouth. ‘ 
When adult, the species reaches a diameter of 11 inches, is quite 
smooth, and is then the Amm. patella, Waagen, whose name must 
now give way to Sowerby’s. It occurs in the “Ironshot Oolite” of 
Dundry, Somerset; and I have a large specimen from Sherborne, 
Dorset. Its horizon is either the Huimphriesianum or Sauzei-zone. 
WITCHELLIA L=VIUSCULA (Sowerby). 
1825. Ammonites leviusculus, Sowerby, Min. Conch. pl. 451, fig. 1, 2. 
1885. Harpoceras leviuseulum, Haug, Beitr. Mon. Harpoceras ; Neues Jahrbuch 
fur Mineral. etc. Beil.-Bd. i. pl. xii. fig. 6. 
Sowerby’s figures of this species are very truthful. They do not, 
however, show one peculiarity belonging to this species, and in fact 
to this genus, namely, that when the test is absent, the ventral area 
carries two deep furrows each side of a carina; when the test is 
present, the furrows are not observable, while the carina is much 
raised, and is of the hollow type. The species occurs plentifully at 
Oborne in the Sauzei-zone, and also at Dundry in the Ironshot Oolite, 
but not so frequently. I have proposed the genus Witchellia for 
species which have the peculiarity of a furrowed core and a hollow 
carina, compressed sides, coarse irregular ribs with a long ventral 
projection, and a suture-line which possesses the characteristics of 
that of Sonninia, but is by no means so ornate. The genus begins 
with the evolute W. Sutneri (Branco), and gradually developing 
ends with the involute W. leviuscula. 
HAMMATOCERAS AMALTHEIFORME (Vacek). 
1886. Harpoceras amaltheiforme, Vacek, Oolithe Cap. San. Vigilio. Abh. k. k. 
geol. Reichsanstalt, Bd. iii. pl. ix. fig. 1 only. 
In youth almost exactly similar to Sonninia corrugata ; but the ribs 
meet the carina with only an extremely slight forward projection. 
When adult, the species is entirely different; it is much thicker, and 
still possesses its coarse ribs. The suture-line is quite different to 
that of Sonninia; the inner lobes crossing the inner area in such an 
oblique direction—much dependent—are characteristic of the genus 
Hammatoceras. 
I possess a whole series showing the evolution of this species from 
Hamm. insigne (Schubler) ; nor does the development of the genus 
end here, for a species with a smaller, almost closed, umbilicus is 
evolved. 
This species occurs in the Concavum-zone of Bradford Abbas, but 
is scarce. 
