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. 



f2 



