224 DR. HINDE AND ME. HOLMES ON SPONGE-REMAINS 



set with spines, at tlie bend of the curve is another group o£ 

 spines, whilst the intermediate portion of the shaft is smooth. 

 Length of spicule '025 mm., thickness (including spines) 

 •015 mm. 



Spirastrella (c). — PI. XII. fig. 7. Spirule with short and 

 strongly curved axis and stout conical spines somewhat thickly 

 set over the spicule and more particularly at the ends, so that 

 its appearance is rather that of a globate. Length of spicule 

 •025 mm., thickness '02 mm. This spicule resembles the spirule 

 of Spirastrella transitoria, Eidley (' Alert ' E-ep. p. 623, pi. liv. 

 fig. (^'), but it is considerably larger. 



Spirular Flesli-Spicules ofPvonSiX, Gray ( = Cliona, 

 Jlancoclc^ pars) . 



Pronax (a). — PI. XII. figs. 8, 8 a. Spicules cylindrical, smooth, 

 truncate at the ends, consisting of four or five inequal twists. 

 Length 'O^ to "046 mm., thickness '0033 mm. These spicules 

 resemble the forms discovered by Hancock in several species of 

 boring sponges, referred by him to Cliona, but subsequently 

 placed by Gray in the genera JPronax and Fione (Proc. Zool. 

 Soc. 1868, pp. 525-6). They approach nearest in outline those 

 oi Cliona gracilis, Hancock (Ann. & Mag. Nat. Hist. s. 3, vol. xix. 

 1867, p. 238, pi. vii. fig. 4). Mr. Carter has figured a similar 

 but larger form in Cliona abyssorum (Ann. & Mag. Nat. Hist. s. 4, 

 vol. xiv. 1874, p. 249, pi. xiv. fig. 33), from the depths of the 

 Atlantic. 



Pronax (b). — PI. XII. fig. 9. Spirule elongate, cylindrical, 

 truncate at the ends, having about six bends or twists ; at each 

 bend or curve there are three or four slender spines projecting 

 outwards, the rest of the spicule appears to be smooth. This 

 form closely resembles the spicules of Pronax {Cliona) lohata, 

 Hancock, sp. (Ann. & Mag. N. H. s. 3, vol. xix. 1867, p. 239, 

 pi. vii. fig. 6) . Similar flesh-spicules are also figured by Eidley 

 in Spirastrella vagalunda and S. congenera ('Alert' Eep. p. 468, 

 pi. xliii. figs. iV, e'), and by Mr. Carter in Bliaphidistia specta- 

 hilis (Ann. & Mag. Nat. Hist. s. 5, vol. iii. 1879, p. 300, pi. xxvi. 

 fig. 14 a). 



