218 GENESIS OF THE ARIETID. 
Lymense as described by Wright. The senile stages separate it from the last, 
though it is probably closely allied, and might be considered a variety if occurring 
in the same bed. Wright’s Wiltshire’, which seems to be identical, was found in 
the Henleyi bed of the Middle Lias. 
SECOND SUBSERIES. 
Oxynoticeras Greenoughi, Hyarr. 
Plate X. Fig. 30. Summ. Pl. XIII. Fig. 13. 
Amm. Greenoughi, Sow., Min, Conch., II. p. 71, pl. exxxil. 
Amm. Greenoughi, Hauer, Ceph. Nordéstl. Alpen, p. 46, pl. xii. 
Amm. oxynotus, Haumr, Thid., pl. xiii. fig. 6, 7 (not fig. 3, 4, 8, 9). 
Amaltheus Greenough, Wrieur, Lias Ammonites, p. 384, pl. xliv. 
Amaltheus Guibalianus, Wrreut, Ibid., p. 385, pl. xlv. 
Amm. Guilbalianus, D’Orz., Terr. Jurass. Ceph., p. 259, pl. xxiii. 
Amm, Guibalianus, Rryniis, Plates (pars). 
Amm. Guibali, Reyniis, Ibid. 
The examination of German specimens led to the conclusion that this species 
was closely allied to oaynotum in development and in sutures, and the splendid 
suite of this species at Semur enabled us to solve all difficulties. 
Here also we were able to compare it with specimens of the true Collenoti, 
D’Orb., the originals of which are in the Museum of Comparative Zodlogy, and 
they have not the slightest claim to be considered identical. Oppel was probably 
led astray by what he supposed to be the types in D’Orbigny’s collection. 
Reynés has divided this species into three forms, not very readily distinguish- 
able by their adult characteristics, but quite distinct when their development 
and old age are studied. His principal observations on Lotharingus, Guibali, and 
Greenoughi were made in the Museum at Semur. We however refer his Guba 
to Greenough, because of their close resemblance in development and old age, and, 
in order to avoid the use of a new name, distinguish the next species, his G'u- 
baliunus, as Guibali. This also is justified by the types in the Semur collection, in 
several of which these names are interchanged. The true Gudbalianus, D’Orb., as 
may be seen by comparison of the original specimen and the Semur collection, 
has more abrupt umbilical shoulders, a more open umbilicus, less involute whorls, 
and retains the keel and typical form of the whorls until a later stage of growth 
than any of the group except oxynotum. 
The shell sometimes attains the size of 235 mm. before any marked change of 
form is observable, and in one specimen reached the size of 410 mm. before the 
keel disappeared. Finally, however, the keel begins to disappear, and eventually 
all traces of it vanish in the rounded abdomen. The form, however, seldom 
changes as completely as in Guibali. The length of the ribs, whether they are 
all long or alternately long and short, is a characteristic of great variability, and 
is of no use in distinguishing the species. 
There are, so far as we have seen, no representatives of this subseries in the 
South German basin, and this observation is sustained by Quenstedt’s “ Ammo- 
niten des Schwiibischen Jura,’ which does not contain a single undoubted form 
