170 UPPER, OR FLINTY CHALK. 



deriving their form from ventriculites, (vide the edge of the flint re- 

 presented in Tab. x. fig. 13.) 



The base forms an elongated stem or stirps, and terminates in diverging 

 root-like processes, by wliich the original was fixed to other bodies ; these 

 are shewn in the specimens represented Tab. xi. fig. 2, and Tab. xii. 

 fig. 2. 



This zoophyte, when contracted into a cylindrical form, is from one to 

 six inches in length ; when expanded, its diameter occasionally exceeds 

 nine inches : the thickness of its substance is seldom more than 0-2 inch. 



Tab. X. represents various flints whose forms are derived from V. 

 radiatus. 



Fig. 1 . This specimen is partially expanded, and its margin exposes 

 casts of the tubuli, as previously mentioned ; the base is perforated by 

 fifteen openings, through which the processes of attachment passed out. 

 A plate of an echinus is attached to the inferior part of the stem. 



Figs. 2, 3, 4. Small turbinated flints, formed in the stirps or base of the 

 funnel-like cavity ; (vide description of Fig. 2, Tab. xi). 



Fig. 5. This elegant flint was discovered by my friend Mr. Thomas 

 Woollgar. The margin is marked with semilunar indentations, the im- 

 pressions of the fibres of the external integument ; a similar appearance 

 is observable on the edge of fig. 9. These markings are peculiar to the 

 fossils of this genus, and attention to tliis circumstance will frequently 

 enable the collector to distinguish the siliceous specimens of ventriculites, 

 from those of Sjjotigus Townsendi. 



Fig. 6. This specimen is inverted in the engraving ; it is hollow, the 

 zoophyte it formerly enclosed having been removed. The uj:)per part 

 (the base of the original) has numerous openings formed by the transit of 

 the radical processes. 



Fig. 7. A transverse section of a flint enclosing the stirps. 



Fig. 8. The thickness of the margin of this specimen, has evidently 

 been produced by the contracted state of the original, at the period of its 

 immersion in the flint. 



