44 SILICEOUS SPONGES. 



Genus SCYTALTA, Zitt. 1878. 



SCTTALIA RADICIFORMIS, PMllips, sp. (Plate VI. figs. 4, 4 «, h.) 



1835. Sponyia racUciformis, Phillips, Geol. of Yorks. p. 90, t. 1. f. 9. 

 1864. Eudea annulata, F. A. Roemer, Palseont. Bd. 13, p. 26, t. 11. f. 2. 

 1878. Scytalia radiciformis, Zitt. Stud. II Ab. p. 64, t. 5. f. 4. 



Sponge either simple or occasionally two individuals growing in close contact, 

 partially coalesce together, elongate, cylindrical, with occasional swellings and 

 constrictions. The summit is conical ; and the body tapers gradually below into 

 a cylindrical stem : the natural termination of this is not preserved. A small 

 specimen measures 65 mm. in length by 22 mm. in width ; and a large example is 

 215 mm. long by 38 mm. wide. 



The characters of the dermal layer cannot be distinguished in the Flamborough 

 examples. The cloacal tube is about 8 mm. in width, and extends about two thirds 

 the length of the sponge ; from the summit-aperture sinuous canals 0"8 mm. wide 

 radiate for a short distance down the cone. In a horizontal section numerous canals 

 about 0"6 mm. in width can be seen extending from the cloacal tube towards the 

 exterior surface of the sponge. The surface beneath the dermal layer exhibits very 

 delicate reticulate fibres which, in specimens from Germany, are seen to be composed 

 of minute, irregularly branched, spinous spicules. 



This species appears to be common. 



Distribution. Upper Chalk : Flamborough ; Ahlten, Hanover. 



Scytalia fastigiata, Lee, sp. (Plate VI. fig. 3.) 



1839. Spongia fastigiata, Lee, Magazine Nat. Hist. vol. iii. p. 14, f. 8. 



Sponge simple, turbinate, with a very prominent conical summit, usually marked 

 ofi" from the main portion of the body by a prominent collar-like ridge. The sponge 

 is widest at the junction of the cone with the body, and diminishes somewhat rapidly 

 to a slight cylindrical stem. The lateral surface exhibits shallow ridges and furrows. 

 An average specimen is 130 mm. in height by 70 mm. in width. 



A smooth dermal layer appears to have covered the entire surface of the sponge. 

 The cloacal tube is 10 mm. wide, apparently cylindrical, and extends nearly to the 

 lower portion of the body. Numerous slightly arched canals 1 mm. in width extend 

 from the cloaca towards the exterior. Similar canals are also exposed on the conical 

 summit, radiating from the cloacal aperture, in specimens where the dermal layer 

 has been removed. These superficial canals by the further growth of the sponge 

 become inclosed, and then appear as interior canals. 



The reticulate fibre of the interior can be distinguished in specimens treated with 

 acid ; but nothing beyond the general Ehizomorine character of the spicules can be 

 recognized. 



