Spongia. ZOOPHYTA. SPONGIADiE. 527 



8. S. Benetlios. — Inversely conical ; hollow externally ; the meshes are ob- 

 long, irregular, and rather distant ; internally with circular depressions ; mar- 

 gin broad, smooth, and nearly flat. — Ventriculites Ben. Mant. Geol. 177- t- 

 xv. £ 3. — In Chalk. 



9. S. subrotundus. — Depressed, subrotund ; central cavity small ; external 

 surface smooth— Choanites sub. Mant. Geol. 179. t. xv. f. 2 In Chalk. 



10. Sflexuosus. — Cyathiform; margin of the central depression marked 



with flexuous indentations ; radical processes long and fibrous. Choanites 



flex. Mant. Geol. 179. t. xv. f. 1 — In Chalk. 



11. S. Koniffii — Inversely conical ; externally marked with irregular fibres, 

 some of which penetrate the substance, and terminate in openings on the in- 

 ner surface ; central cavity cylindrical, deep, narrow ; base fixed by radical 

 processes— Choanites Kon. Mant. Geol. 179. t. xvi. f. 19 In Chalk. 



Many other species are obscurely announced in Park. Org. Rem. ii. (1.) 

 p. 95. t. ix. f. 4. ; (2.) p. 100. t. ix. f. 1. ; (3.) p. 130. t. xi. f. 4. ; (4.) p. 132. t. 

 xh. f. 5. ; (5.) p. 133. t. xii. f. 7. ; (6.) p. 102. t. ix. f. 9. 



The resemblance of these fossil bodies to the recent species of sponges is 

 very considerable, and would justify any one acquainted with the structure 

 of the latter, to refer the whole to the genus Halicfwndria. The forms of 

 the recent species, however, are variable, and the utmost caution is requisite 

 in establishing species founded on so vague a character. Yet Dr Mantell, 

 otherwise a sagacious geologist, has not hesitated to adopt two new genera, 

 Ventriculites and Choanites, depending on the form of the substances contem- 

 plated, and to which, while recent, he has, in the absence of all proof, some- 

 what incautiously, assigned an expansive and contractile power. It is in- 

 teresting to observe the remains of the radiated siliceous spicula } r et preserved 

 in stone, as has been demonstrated by Mr Parkinson, in liis Org. Rem. ii. 95. 

 t. vii. f. 8. 



