122 SILICEOUS SPONGES. 



is -3 mm. The ridges of the outer surface of the wall of this species are more slender 

 than in C. Beneftim, and the form itself is smaller. 

 Distribution. Upper Chalk : South of England. 



Cephalites bullatus, Toulm. Smith. (Plate XXVII. figs. 3, 3 «, 3 b.) 



1847-48. Cephalites bullatus, T. Smith, Ann. & Mag. Nat. Hist. 1st ser. vol. xx. t. 7. f. 3, 



and 2nd ser. vol. i. p. 284, t. 14. f. 6. 

 1816. Flint Alajonite, W. Smith, Strata identified by Org. Fossils, p. 7, t. 3. f. 2. 



Sponges with a funnel-shaped or subcylindrical body, about 36 mm. in length, and 

 from 21 to 36 mm. in width, supported on a delicate stem, with divergent rootlets at 

 its termination. The wall varies from 5"5 to 12 mm. in thickness. 



The wall of the outer surface is folded in such a manner as to form, on the sur- 

 face of perfect specimens, small, flat-topped, lozenge-shaped or irregular projections, 

 about 4 mm. wide, which are disposed in quincunx. The dermal membrane of these 

 projections is minutely porous, and small, hollow, occasionally bifurcating, spines 

 spring from its surface. The interior surface of the wall is perforated with circular 

 or elliptical canal-apertures about 2 mm. in diameter. The plaits of the interior 

 portion of the wall are about -8 mm. in width ; they are disposed in deep folds 

 extending from the outer nearly to the inner surface, and vice versa; they also 

 form occasional loops. 



This species is distinctly characterized by the features of the outer surface. 

 T. Smith's figured specimen does not appear to be in the Museum Collection, but 

 there are several examples labelled by him from which the above description has 

 been taken. It appears to me very doubtful if the forms referred to this species by 

 Reuss* and Quenstedtf really belong to it. 



Distribution. Upper Chalk : South of England {coll. T. Smith). 



Cephalites catenifer, Toulm. Smith. 



1848. Cephalites catenifer, T. Smith, Ann. & Mag. Nat. Hist. 2nd ser. vol. i. p. 286, t. 14. 



f. 14, 15, 16. 

 1848. Cephalites covipressus, T. Smith, ib. p. 287, t. 14. f. 10. 

 1877. Toulminia catenifer and compressus, Zitt. Studien, I Ab. p. 56; Neues Jahrbuch, 



p. 368. 



Sponges funnel-shaped or inverted conical, supported on a slender stem. An 

 average example is 48 mm. in length and 34 mm. in width ; the stem appears to 

 have been about 15 mm. in length. The wall is from 11 to 14 mm. in thickness. 

 The outer surface of the wall is composed of ridges about 1-8 mm. in width, 



* Yerst. d. bohm. Kreide, II Ab. p. 74, t. IS. f. 11. 

 t Petref. Bd. 5, p. 4S4, t. 138. f. 10, 11. 



