]12 SILICEOUS SPONGES. 



funnel- or cup-shaped. A slender cylindrical stem with branching roots is usually 

 present, but in some examples the root-processes spring directly from the base of the 

 funnel. The specimens vary from 50 to 120 mm. in height and from 20 to 75 mm. 

 in width. The outer surface of the sponge-wall is folded into vertical ridges about 

 2*8 mm. in width, and these are divided transversely so as to form so many rows of 

 rounded projecting wart-like bosses. The inner surface of the wall, according to 

 Toulmin Smith's figure, appears to be composed of simple open furrows and ridges ; 

 but in none of the Museum specimens is the inner surface of the wall distinctly 

 shown, aud it cannot be seen in the type specimen from which T. Smith's figure has 

 been drawn, so that this portion of the figure is purely imaginary. In a specimen 

 preserved in flint the thickness of the wall is 4 mm. 



The spicules of the interior mesh have conspicuous lantern or octahedral nodes ; 

 the spicular rays are about "25 mm. in length. 



This species differs from V. decurrens mainly in the warty projections of the 

 outer wall. 



Listrihution. Upper Chalk: Sussex {coll. T. Smith and Mantell). 



Ventriculites infundibuliformis, S. Woochoard. (Plate XXVI. figs. 1, 1 a.) 



1833. Ventriculites infundibuliformis, S. Woodw. Geology of Norfolk, t. 4. f. 20, 21. 



1848. Ventriculites bicomplicatus, T. Smith, Ann. &. Mag. Nat. Hist. 2nd ser. vol. i. 



p. 219, fig. E. 

 1848. Ventriculites latiplicatus, T. Smith, ibid. p. 215, fig. D. 

 1848. Ventriculites striatus, T. Smith, ibid. p. 212, t. 13. f. 6, 13. 

 1848. Ventriculites radiatus, T. Smith (non Mantell), ibid. p. 218, t. 13. f. 10, 15. 



Sponges elongated funnel-shaped, sometimes laterally compressed above, or slightly 

 exp;iuding outwards ; the divergent roots spring from the basal end of the funnel. 

 The total thickness of the wall is from 7 to 8-5 mm.; the plaits forming the wall are 

 about 1 mm. in thickness. I have not met with a complete specimen ; the greatest 

 width at the summit of an individual is 83 mm. 



The exterior surface is composed of rounded, occasionally bifurcating ridges, about 

 1-8 mm. wide, which extend vertically from the base to the summit, and are connected 

 laterally so as to leave narrow oval interspaces about 4 mm. in length by 1"25 mm. 

 in width, which are sometimes disposed in quincunx. The inner surface of the wall 

 is rarely exposed ; it appears to be similar in character to the outer surface. 



The spicular mesh is only shown by the empty moulds of the spicules in the 

 Chalk ; it appears to be irregular, with prominent octahedral nodes ; the distance 

 from node to node is '38 mm. 



The aspect of this species varies greatly, according as it happens to be preserved 

 in the interior of flints or in chalk. As a general rule only the lower portions of 

 the sponge are met with in flints, and these specimens do not show the oval inter- 



