184 DE. HINDE AND ME. HOLMES ON SPONGE-EEMAINS 



Length •12--3 mm. by •013--024 mm. in thickness. Spicules 

 similar to fig. 13 but less robust occur in Gladochalina nuda, var. 

 ahruptispicula, Ridley (' Alert ' Eep. (1884) p. 396, pi. xli. fig. J), 

 from Torres Straits. 



PL VII. figs. 31-36. Cylindrical spicules, smooth, evenly curved, 

 with rounded non-iuflated ends. They are of very varying length, 

 the smaller forms so reduced as to become reniform (fig. 32). 

 The axial canals but seldom shown. Length from '025 to -195 mm. 

 by •014-'03 mm. in thickness. Spicules of this type are common 

 as fossils from the Carboniferous formation upwards, but the 

 older forms are generally much larger than the Tertiary and 

 Eecent. A recent sponge with similar spicules from the Grulf of 

 MaDaar is referred by Carter to Beniera (Aun. & Mag. IST. H. 

 s. 5, vol. vi. p. 48, pi. V. fig. 18). 



PI. VII. fig. 46. Cylindrical, smooth, nearly straight, ends 

 evenly rounded, to a slight degree thicker near the ends than in 

 the central portiou of the spicule. Length -87 mm. by '02 mm. in 

 thickness. Spicules of this type are present in Beniera, Myxilla, 

 and other genera. The spicules of the existing Beniera cratera, 

 Osc. Sch. (Spong. Adriat. p. 73, pl.vii.fig. 7), are closely similar. 



PI. VII. figs. 45, 47. Cylindrical, smooth, elongate, slightly 

 curved, ends obtuse or rounded. Length '26 to '37 mm. by -005 

 to "006 mm. in thickness. Similar but slightly larger spicules 

 are present in Baspailia tenuis, Eidley & Dendy (Chall. Eep. 

 vol. XX. p. 188, pi. xl. fig. 8&), from near Bahia in shallow waler, 

 and they occur detached in dredgings from off" the S.W. coast 

 of Australia, at a depth of 2479 fathoms. 



PI. VII. figs. 23-25. Smooth, fusiform, acerate spicules, 

 straight or slightly curved, with a well-marked central bulbous 

 inflation. The axial canal is continuous throughout the spicule, 

 with a very slight central inflation. Length from -1 to '32 mm. 

 by •013--03 mm. in thickness. Similar spicules are figured by 

 Bowerbank in Isodictya anomala (Mon. Brit. Spong. iii. pi. 1. 

 fig. 3) and by Carter in SalicJiondria aceratospiculum (Ann. & 

 Mag. N. H. s. 5, vol. vi. pi. v. fig. 19 h) ; also by Hansen in 

 Cladorhiza alyssicola, Sars (jSToriv. North-Atl. Exp., Spong.pl. iv. 

 fig. 4). 



Spined Skeletal Spicules of various Genera. 



PL VII. fig. 15, Eusiform, curved, very gradually taperiug, 

 thickly spined throughout ; spines small, without arrangement. 

 Axial canal opening at both ends. Similarly spined but smaller 



