ialontolngia ndita,

194:
REVISION OF THE JURASSIC CE}»HALOPOD
Pl.BUBOCEPHA.LITEB ELEPHANTINUS (J. de C. Sowerby).
(PI. XXIII, fig. 3 ; pi. XXIV, . figs. la, b ; pi. XXXI, figs-. 2a, b).
1840. Ammonites elephantinus J. de C. Sowerby, pl. XXIII, fig. _
6.
1889. Stepfw,noceras herveyi (J. Sowerby) ; Newton, p. 334, pars (non pl. XIV, figs. 1-2).
1898. · Macrocephalites elephantinus (Sower by) ; Skeat and Madsen, p. 105.
1902. Ammonites elephantinus (Sowerby) ; Blake, p. 35.
1910. Macrocephalites elephantinus (Sowerby) ; Lemoine, p. 29 (non 36).
1925. "Stephanoceras herveyi " (Sowerby) ; Newton ; Spath (b), p. 27.
fWn 1875. Stephanoceras elephantinum Waagen, p. 124, pl. XXXI, figs. 3, 3a ; pl.
XXXII, figs. 4a-c.
non 1924. Dkosaites elephantinus (Waagen) ; Spath, p. 10.
non 1928. Macrocephalites elephantinus (Sowerby) ; Nickles p. 34.
This species was confused by Waagen with the Dhosa Oolite form described
below as Dhosaites elephantoides and it has since generally been misinterpreted
in geological literature. ,Before I examined Waagen's original I
thought the two forms differed merely in the peripheral projection of the ribs
and in proposing the genus Dhosaites for the ' elephantinus-group ', I was relying
mainly on the Mayaites-like earlier whorls represented in the Blake Collection.
These resembled Waagen's small example (pl. XXXII, fig. 4) but
could not easily be compared to Sowerby's holotype on account of difference
in size. The latter, ·after tedious preparation, has now yielded at least part
of the suture-line ; and with the information derived from a dozen examples
,since sent by Mr. J. H. Smith, its systematic position can at last be fixed.
The majority of the specimens are intermediate to P. habyensis, with straighter
ribs and smaller umbilicus, an cannot be distinguished from the MadagascJ.n
form figured by Lemoine (1910, pl. II, figs. 3a, b only). The type itself is
till more extreme and the peripheral sinus is well-marked. It is, however,
.doubtful whether the (inaccessible) inner whorls of Sowerby's type agree with
the small example here reproduced (pl. XXXI, figs. 2a, b) which is taken to
represent the immature K. elephantinus. On the body-chamber (not here figured)
of the example, at a diameter of about 65 mm., the ribbing is perhaps less
coarse and slightly closer than in the type, but there is considerable variability
among the material available, especially in the amount of peripheral projection
at various diameters, so that with less abundant material one might be led
into naming individuals instead of species.: All these forms show such a striking
resemblance · to the later Epimayaites subtumidus (Waagen), e.g. the examples represented
in pl. XXXI, fig. 7 or pl. XXV, fig. 5, that the citation of ' Maoroephalites
subtumidus from Callovian · deposits, for example from Chanaz, Savoy (Parona
and Bonarelli, 1897, p. 155) or Villany (Loczy, 1915, p. 353} is easily explained.
There are, however, still other developments that have been mistaken
for the Kachh form, e.g. South American Eurycephalites and immature Europea-n
Moorocephalites of the rotundus and- eszterensis types (Simionescu, 1905, p. 33,
pl. Ill, fig. 6 and Popovici-Hatzeg's 'Sphaeroceras ymir ' [Oppel], 1905, p. 22,
pl. VI, figs. 8-9), easily recognisable by their intricate suture-lines (compare
pl. XXXIII, fig. 4), or Pleurocephalites (Bukowski, 1886, p. 127).