ialontolngia ndita,

FAUNA OF KACHH (CUTCH). 19!
.ments. The external lobe is as deep · as the first lateral. Some forms of
Mayaites of the jumarensis type show superficial resemblance to the present
species and the occasional reference of Callovian Macrocephalitids to the Argovian
Mayaites (see e.g. Stehn, 1922, p. 85) may be due to this similarity of
outer whorl-fragments ...
Horizon.-Lower Callovian, dimerus or diadematus zone.
Locality.- -Jumara (beds 9-11, Blake Coll ction No. 229).
INDOCEPHALITES SPHAEROIDALIS, sp. nov.
(PI. ·xxv, fig. 3, pi. XXVI, fig. 1, pi. XXVII, fig. 2).
1913. Stephanoceras sp. (ball-shaped) ; Smith, p. 210 (bed 1).
This form is available in only a single specimen · but it is now given a
new name because it seems to form an important 'link between the group of
· lndocephalites chrysoolithicus on the one hand and Kamptokephalites dimerus
on the other, the inner whorls resembling the latter, the outer the former
species. The suture-line, however, (pl. XXVII, fig. 2) is that of an Jndocephalites,
and the outer whorl, unfortunately too poorly preserved to be · figured,
is comparable to that of large and equally sphaeroidal _and involute I. chrysoolithicus
whilst the resemblance to Kamptokephalit dimerus and certain passage
_
forms . to Pleurocephalites habyensis is co;nfined _to a similar sharp costation of
the inner whorls, combined with an open up1bilicus at that . stage. The umbilical
wall is then vertical and its edge comparatjvely well-defined, . with the
region of greatest whorl-thickness in close proximity, giving the section a semi-
_lunar shape. The periphery then is also more depressed a:pd more flattened
than in I.. chrysoolithicus and the ribs describe a sinus forward in _ the middle
of the ventral area.
On -the outer whorl, however, still _ septate at 110 mm .. diameter, the umbilical
wall has become lower nd more rounded with thnow far less distinct--primary
ribs _ beginning app rently some distance from the smooth umbilical
slope. T}ris outer whorl is worn but since the details of the suture-line
.are visible, not much of the umbilical slope cn . be missing. The · appearanceat
that stage is like that of the ..transitional lndoeepites figured in pi. XXIV,
fig. 7, but the pri)nary ribs appear closer and less _distinct7 whilst the secondaries
seem more distant_ and proportionately stronger.. There are still three
.secondaries, however, to each primary and the difference is not of importance.
On the . other han.d the umbilicus is smaller.. 'l;he proportions of the figured
inner whorls are :-60 - ·43. - ·57 - ·27 ; with the septate outer whorl add.ed
they. a:::e .:-1 10 - ·58 - ·51 - ·14. This change in whorl-shape as well as . the
macrpcephalitid outer whorl indicate closer relationship of the present . form
with lndocephalites rather than the group . of . Kf;tmptokephalites dimerU&.
Horizon .. ..__Lower CalJovian, dimerus zone.