STAUEONEMA. 99 



The large dimensions of this species, and the size of the tubes and walls, readily 

 distinguish it from all others of the genus. The only specimen is in Chalk Marl, 

 and the spicular structure comes out very perfectly when the matrix is removed 

 by acid. 



Distribution. Chalk Marl : Ventnor, Isle of Wight {MantelVs coll.). 



Genus STAUEONEMA, Sollas, 1877. 



Staueonema Carteki, Sollas. (Plate XXIV. figs. 1, 1 a, 1 b.) 



1877. Stauronema Carteri, Sollas, Ann. & Mag. Nat. Hist. vol. xix. p. 1, t. 1-5. 

 1877. Stauronema Carteri, Zitt. Studien, I Ab. p. 62; Neues Jahrbuch, p. 359. 



Examples of this species in the Museum collection from the Chalk Marl of Barham 

 and the Isle of Wight, and from the Craie Chloritee of Cap la Heve, show the minute 

 spicular structures in a much clearer manner than the specimens from the Upper 

 Green Sand of Folkestone, on which Prof. Sollas based his descriptions ; and they 

 enable me to add to, and partly to emend, the characters which he has assigned to 

 the species and genus. 



The canals which pass into the true wall (oscular plate, Sollas) from the inner or 

 concave surface of the sponge, do not appear to penetrate through it, as stated by 

 Sollas, but terminate blindly near the outer surface of the sponge, and, similarly, the 

 canals which enter the wall from the outer surface end blindly in the substance of 

 the wall. The canals in the supplemental skeleton (posterior mass) are altogether 

 irregular in their distribution. The spicular mesh of the true wall is by no means 

 so regular in its disposition throughout as represented by Sollas in figs. 1-3, p. 7, 

 loc. cit., for though the mesh-interspaces are often circular, yet they are as often 

 quadrate, oval, or irregular in form. 



Again, Sollas states (p. 7) that " the outer margins of the fibres are so sharply 

 defined as to enable us to state with certainty that the fibres themselves are perfectly 

 smooth, and not in any way spined." But in the example from La Heve, not only 

 are the surfaces of the spicules bordering the canals thickly spined, which Sollas 

 observed in the Folkestone examples, but the spicular arms throughout the wall and 

 in the supplemental skeleton are clearly microspined. A remarkable feature in this 

 species is the supplemental skeleton (posterior mass, Sollas), which is composed of a 

 spicular mesh, with arms or rays of about the same thickness as in the true wall, but 

 disposed in such a manner that the interspaces are extremely irregular, both in size 

 and form. This tissue appears to be of a similar character to that which in some 

 fossil sponges forms the stem and radical processes, and also grows over the lower 

 portion of the true sponge-wall. It is shown more particularly in the genus Pleurope, 

 Zittel, and is well developed in Craticularia (Laocoetis) infundibulata*, Pomel. The 



* Pal. d'Oran. 1866, p. 95, t. 1 bis, fig. 4. 



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