THECOSIPHONIA. 75 



Genus THECOSIPHONIA, Zittel, 1878. 



Thecosiphonia nobilis, Roemer, sp. (Plate XVII. figs. 3, 3 a.) 



1864'. Limnorea nobilis, F. A. Roemer, Palseont. Bd. 13, p. 37, t. 15. f. 1. 

 1878. Limnorea nobilis, Quenst. Petref. BJ. 5, t. 133. f. 8-11. 

 1878. Thecosiphonia nobilis, Zittel, Studien, II Ab. p. 84. 



The only example of this species is a compound form, 72 mm. in height by 90 mm. 

 in width, consisting of three individuals closely aggregated together, and united by a 

 common dermal layer. The individuals are roughly ovate in form ; they appear to 

 have had one or two cloaca-like depressions on the summit ; the canal-structure of 

 the interior has been destroyed. Some of the spicules of the interior mesh can be 

 seen ; they are relatively very large, the arms and nodes measuring 5 mm. in length ; 

 the nodes are very prominent. 



The dermal layer is thin, and grows in concentric, wrinkled bands ; it appears to 

 have originally extended all over the sponge, with the exception of the summit ; its 

 surface is smooth, and contrasts strongly with the rough furrowed character of the 

 summit. I have been unable to determine the form of the spicules composing this 

 membrane. 



Distribution. Upper Chalk : Wiltshire {Cannington coll.). The example belongs 

 to the Jermyn-Street Museum. 



Thecosiphonia turbinata, Hinde, n. sp. (Plate XVII. fig. 4.) 



Sponge turbinate in form ; the upper portion or body is depressed, conical, with a 

 wide base supported on a short, oblique, obtusely terminated stem. The base is 

 concentrically furrowed and wrinkled, and carries one or two short radical processes. 

 The single example is 85 mm. in height and 100 mm. in width. 



The upper surface of the sponge is rough ; the cloaca at the summit is 26 mm. in 

 width, and does not appear to have been deep ; from its margins sinuous branching 

 canals radiate over the surface. The interior canals have been destroyed. 



Only here and there can the four-rayed spicules of the mesh be detected ; they are 

 smaller than those of T. nobilis. The under surface and the stem appear to have 

 been completely covered with the dermal layer, but its spicular elements cannot be 

 recognized. 



The only specimen is now a mass of flint, in which only the outer form, the dermal 

 layer, and a few of the interior spicules are preserved. In its form and in the 

 restriction of the dermal layer to the basal portion it differs from Thecosiphonia 

 {Tremosjjongia) grandis, Roemer*. 



Distribution. Upper Chalk : Stockton, near Heytesbury, Wiltshire. 



• Palicontogr. Bd. 13, Taf. 15. fig. 3c. 



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