1872..
S0LLAS — UPPER-GEEENSAND VENTRICULITES.
(iv.) On the fibre between two elements at the ordinary distance
from each, other, the centre of an apparently superfluous element
unexpectedly appears. Of its four radii seen in the section, two of
course are parts of the fibre on which the centre occurs ; the other
two normally have no radii with which they can combine, and as a
consequence they bend away in opposite directions at about 45° from
their fellows, and open into the octahedral fibres of adjacent hexra-
diate elements (fig. 5). Besides these, other variations occur (fig. 6).
Fie. 5.
Fig. 6.
Spicules. — Though siliceous spicules are well preserved in some
flints and coprolites, yet a careful examination has failed to reveal
their presence in silicified ventriculites (T. Smith) or in phospha-
tized ones. For all this the Ventriculites may have been spiculate
sponges ; in a section of a Bronchiolites, and in one of V. tessellatus,
I have found simple acerate spicules, with which were associated one
or two hexaradiate ones ; possibly, however, these may have been
washed in from the sea-bed during; fossilization.
Identification of Species.
i. Ventriculites tessellatus (Toulmin Smith) ; Scyphia tessellata
(Seeley); Spongia texturata (Quenstedt).
Quenstedt' s figure * of this species is an excellent one ; it is
taken from a specimen from the Weisse Jura, and accurately repro-
duces the Cambridge form. Quenstedt refers Scyphia texturata
and S. parallela (Goldfuss) to the same species t, as well as Alcyon-
ites texturatus (Schlotheim t and Parkinson §). This latter identi-
fication appears to me very questionable, Parkinson's figure more
nearly representing Ventriculites quincuncialis than V. tessellatus.
In the Eoyal College of Surgeons is a specimen from the Jurassic
of Wiirttemberg, labelled by Prof. Morris, Ventriculites texata
(Miinster), which is in every respect a fac-simile of our Cambridge
species ; and I believe S. tessellata (Seeley), S. texturata (Quenstedt),
and V. texata (Miinster) are identical with V. tessellatus (T. Smith).
The following is a description of our Greensand Ventriculites tessel-

• Der Jura, Quenstedt, tab. 83. fig. 7, p. 683.
  

t Petref. Germ., Goldfuss, tab. 2. fig. 9, tab. 3. fig. 3.
J Petref., Schlotheim, p. 373.
§ Parkinson, 'Organic remains,' tab. 10. fig. 12.