Ser. XV. HIMALAYAN FOSSILS, Vol. IV. THE FAUNA OF THE SPITI ...

HOPLITES.
The costate forms of the Neocomian Hoplites may be divided into the
lowing groups and subgenera :—
!•—The Group of HOPLITES PEXIPTYCHUS.
KILIANELLA, nov. subgenus.
Small forms with a comparatively simple suture-line. There occur fairly
distinct, and frequently even deep constrictions. The ribs are either shghtly or
decidedly falciform: starting from the umbilical wall they run in a straight
Tadial direction up to about the middle of the volutions and then bend suddenly
and decidedly backwards, and only close to the ventral face do they again assume
a forward inclination. Certain ribs split up at half the volution-height, others
ran undivided from the umbilicus to the external margin. In some forms the
simple ribs exceed the branching ones in number. The large majority of the
ribs originate singly on the umbilical wall, and only a few ribs start as ribpairs.
In some forms a weak tubercle or a slight thickening marks the branching-points
of the ribs. The external margin is smooth, and it is bordered on
either side by the rib-terminations which are thickened and often also broadened
and bear a small tubercle. The cross-section of the volutions is comparatively
low, and is elliptical or rounded-octagonal in shape. The shell is rather flat
and possesses a wide umbilicus.
The following Indian species belong to the subgenus Kiliandla :—
Kilianella pexiptycha Uhlig (pi. LXXXII, fig. 2).
,, constricta n. sp. (pi. LXXXII, fig. 5).
,, n. sp. ind. aff. epimeloides Parona sp. (pi. LXXXYI, fig. 5).
n. sp. ind. (pi. LXXXII, fig. 4).
,, leptosoma n. sp. (pi. LXXXII, fig. 3).
Of these species • K. constricta is distinguished mainly by its exceedingly
deep constrictions, K. n. sp. aff. epimeloides by the pronounced backward inclination
of its somewhat irregular ribs, K. sp. ind. by the distinctly falciform shape
of its individual ribs.
The following European and African species may also find place in this
group :—
Kilianella pexiptycha Uhlig ( = Hoplites Roubaudi d'Orbigny, teste Kilian).
,, aspemma d'Orbigny sp.
„ cf. asperrima d'Orbigny (Uhlig).
„ sinuosa d'Orbigny sp.
„ epimeloides (Mgh.) Parona.
„ I saris. Pomel sp.
„ Roubaudi Pavlow.
r- • French palaeontologists place Kiliandla pexiptycha in the group of Hoplites
-!'neocomiensis. r According to. Kilian the distinction between Hoplites neocomiensts
with' distantly spaced ribs and Hoplites pexiptychus with finer ribs is not always
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