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

HOPLITES. Jtf!
Carpathians in Silesia. To these scanty representatives we are abl* U> add a v w
what greater number of species from the Himalaya, namely :—
Sarasinella varians n. Bp.
,, subspinosa n. sp.
2 n. sp. ind. aff. subspinosa n. sp.
,, n. sp. aff. ambigua Uhlig.
The Asiatic forms are closely related to the European ones, which leads
us to the conclusion that we have to deal here with a well individualised branch
of the genus Hoplites, whose evolutional direction deviates from that of the
other Hoplites groups. This fact calls for the establishment of a separate sub-
genus, on which we bestow the name of Sarasinella. l
With this subgenus we may provisionally classify three forms whose orna-
mentation consists exclusively of forked ribs united into bundles, and amongst
which a trituberculate stage has not yet been detected up to the present. These
forms are Hoplites Cautleyi Oppel sp. (non Spiticeras Cautleyi Oppel sp.) from the
Spiti Shales, Hoplites teschenensis from the Valanginian of the Carpathians of
Silesia and Hoplites fascicularis d'Orbigny sp. Unfortunately these species are
only imperfectly known, and consequently we are not able to arrive at a de-
finite conclusion with regard to them. It is possible that they represent types
which outgrow the trituberculate stage at an early period of their existence or
have even eliminated it entirely from their ontogenetic development. Hoplite*
campylotoxus Uhlig may be looked upon as a transitional form, in so far as in
this species traces of lateral tubercles are yet recognisable, which, in the forms
referred to above, are entirely wanting. Or we may conceive that the forms
in question are derived from Aulacostephanus, with some such form as Aulacoste-
phanus progenitor Zittel as an intermediate link. Their resemblance to the full-
grown stage of Sarasinella would then have to be regarded as a case of conver-
gence. Considering the scantiness of the available material this question cannot
be decided definitely for the present. We propose therefore to include these
interesting forms provisionally in the subgenus Sarasinella.
Certain relations exist between this subgenus and a remarkable, large-sized
form from the Lower Neocomian of Silesia, ' namely, Hoplites austro-silesiacus
Uhlig. In this species also the primitive trituberculate sculpture is replaced on
the last volution by a costate ornamentation. The ribs, however, which con-
stitute the latter, are not gathered into bundles, but originate singly and sub-
divide into branches on the upper part of the flanks. It is probable that this
form also represents a small lateral outgrowth, the evolution and significance-
of which cannot be clearly appreciated at present.
1 Named in honour of Professor Ch. Sarasin of Geneva.
a