116 SILICEOUS SPONGES. 



Genus EHIZOPOTERION, Zittel, 1877. 

 Rhizopoterion cervicorne, Goldf. sp. 



1826-33. SipJwnia cervicornis, Golclf. Petref. 1 Th. p. 18, t. 6. f. 11, and p. 98, t. 35. £. 11. 



1877. Rhizopoterion cervicorne, Zitt. Studien, I Ab. p. 51; Neues Jahrbuch, p. 362, t. 3. f. 6. 



1878. Siphonia cervicornis, Quenst. Petref. Bd. 5, p. 422, 1. 135. f. 9. 



Two specimens of the stem and roots of a sponge preserved in flint probably 

 belong to this species. The spicular structure has not been preserved, but the 

 longitudinal canals very closely resemble those of typical examples from Germany. 



Distribution. Upper Chalk : England ; Bromberg, Haldem, Germany {coll. Zitt.). 



Genus SPOEADOSCINIA, Pomel, 1872, emend. Zittel, 1877. 

 Sporadoscinia micrommata, Boem. sp. 



1840. Scyphia micrommata, F. A. Roemer, Nordd. Kreide, p. 7, t. 2. fig. 11. 

 1872. Cribrosjjongia micromata, Schliiter, Spongit. des Miiusterlandes, p. 28. 

 1877. Sjjoradoscinia micrommata, Zitt. Studieiij I Ab. p. 52; Neues Jahrbuch, p. 362, 

 t. 3. f. 5. 



Sponges cup-shaped or forming slightly concave expansions, supported on a short 

 inverted-conical, hollow, basal portion. No root-processes have been preserved. 

 The thickness of the wall is only 1 mm., but all the specimens have been replaced 

 by peroxide of iron, and it is probable that the wall has suffered from compression. 

 The height of a specimen is 45 mm. and the width across the summit is 105 mm. 



The outer surface is furnished with irregularly disposed, circular or transversely 

 ovate apertures, about '9 mm. in width, and the same or a slightly greater distance 

 apart from each other ; the inner surface of the wall has elliptical apertures, about 

 1-3 mm. in length, disposed regularly in quincunx. No spicular structure has been 

 preserved. The dermal layer appears to have been minutely porous. 



Distribiotion. Upper Chalk ; Bromley, Kent (coll. T. Smith), 



Sporadoscinia Decheni, Goldf. sp. 



1826-33. Scyphia Dechenii, Goldfuss, Petref. 1 Th. p. 219, t. 65. f. 6. 



1877. Sporadoscinia Decheni, Zitt. Studieu, I Ab. p. 52 ; Neues Jahrbuch, p. 362. 



1878. Scyphia Dechenii, Quenst. Petref. Bd. 5, p. 454, 1. 137. f. 2. 



Microscopic fragments of the spicular structure of this species from the Upper 

 Chalk of Coesfeld, Westphalia. 



Sporadoscinia capax, Ilinde, n. sp. (Plate XXVI. figs. 4, 4 «, 4 b.) 

 Sponge open funnel-shaped, growing to a large size ; no stem has been preserved. 

 The wall is 5 mm. in thickness; it is possible that it may have been originally of 



