20 SILICEOUS SPONGES. 



These spicules retain their siliceous condition ; some are crypto-crystalline, others 

 are distinctly crystalline. In these latter the central canal is occasionally preserved. 

 They now occur detached. Mr. Carter regards them as probably allied to existing 

 large-spiculed Renierida ; they are very much larger than any existing forms. For 

 the sake of reference I have placed them provisionally under the genus Eeniera, and 

 associated them with the name of Dr. H. J. Carter, who first described and figured 

 them. 



Distribution. Carboniferous Limestone : Dairy, Ayrshire. 



Genus DIRHHOPALUM, Eidlei/, 1881. 

 DiRKHOPALUM PLANUM, Hinde, sp. 

 1880. Reniera, sp., Hinde, Foss. Sponge-spicules, p. 21, t. I. f. 18, 19. 



Detached spicules of a conical form, widest at the summits, which are rounded, 

 and gradually tapering to a pointed or blunted extremity. The interior exhibits a 

 relatively large canal of a conical form. The surface appears to have been smooth. 

 In length these spicules vary between 0-495 and 0-832 mm., and the width at the 

 summit from O'lSS to 0-225 mm. Abundant in the interior of flints. 



I had referred these spicules to a species of Reniera ; but Mr. Ridley * has suggested 

 their resemblance to the peg-top spicules of Dirrhopalum (Plocamia) clojpetariwu, 

 O. Schmidt f; and though the fossil spicules are much larger than those of the 

 existing species, the similarity of form may indicate a relationship, and I therefore 

 place them in this genus until more is known of their afiinities. Spicules of a 

 similar form, but with tuberculated or spinous surfaces, are also present in the 

 Chalk, and it is at present uncertain whether they belong to the same sponge as the 

 smooth forms. Prof. Sollas has given to the spinous forms the name of BJwpalo- 

 conns tulercidatiisX. 



Distribution. Upper Chalk : Horstead, North of Ireland ; Coesfeld, Westphalia. 



Genus ACANTHORAPHIS, Binde, gen. nov. 

 AcANTHOEAPHis INTBRTEXTDS, Hinde, sp. nov. (Plate I. figs. 3, 3«.) 

 Sponge apparently of an ovoid shape ; the single example is 25 mm. in length 

 by 16 mm. in width. The only structure preserved is a thin delicate surface- 

 tissue with subangular apertures, about 0-75 mm. wide, and porous interspaces 

 between them. This tissue is foraied by a layer of straight spicules, superposed over 

 each other in an irregular manner, but not apparently in any way attached to each 

 other. The spicules are fusiform, gradually tapering from the centre to each end ; 

 their surfaces are covered with minute blunted spines. They vary somewhat in 



* Joum. Linn. Soc. vol. xv. p. 487. t Spong. Atlan. Gebiet. p. 63, t. 4. f. 18. 



J Ann. & Mag. Nat. Hist. ser. 5, vol. vi. p. 392. 



