336 



Anatomy of the Ventriculites of Mantel. 



bottom of the conical cavity of a nodule of flint ; and, in this 

 degree of expansion, the orifices of the tubes still remain con- 

 cealed ; the cavity of the nodule displays the arrangement of 

 those orifices, and renders the representation of a fully ex- 

 panded animal unnecessary. In Mr. Mantel's work (tab. 14. 

 fig. 1.) a chalk specimen is represented, vi^here the animal is in 

 complete expansion, exhibiting the perforated papillae. I 

 possess a similar one in flint. 



The concentric lamince compose the chief substance of the 

 animal ; the inner layers are cribriform, from the passage of 

 the numerous tubes originating in the ventricular cavity, and 

 passing transversely, previously to taking their course longi- 

 tudinally towards the lower extremity or centre of the animal. 

 These laminae are composed oi fibres passing in a radiated 

 form, from the centre to the circumference, crossed by others 

 transversely, and, consequently, in a circular form, and thus 

 constructing a retiform parenchyma; in the contracted state 

 of the animal, these fibres are moniliform, being thus ex- 

 hibited in silicious spe- 

 cimens, as shown in 

 fig. 95. a. The con- 

 centric arrangement of 

 these layers is exhibited 

 in a slightly magnified 

 delineation of a silicious 



specimen m my posses- 

 sion, [fig. 96. ) * It is 

 difficult to ascertain 

 the thickness of this 

 middle texture, or that 

 of the perfect animal 

 mineralised ; its remains 

 varying so much in 

 density, and in the pro- 

 portions, or parts pre- 

 served. Mr. Mantel 

 says, " this zoophyte, 



96 .^-^^^r^ when contracted into a cylindrical form, 



is from 1 to 6 in. in length ; when 

 expanded, its diameter occasionally ex- 

 ceeds 9 in. ; the thickness of its sub- 

 stance is seldom more than 0*2 in." 

 I possess a fully expanded silicious spe- 

 cimen whose diameter is 7^ in. 

 The tubes originate in the texture of 



It is a transverse section of a specimen in flint. 



