EEPOET ON THE HEXACTINELLIDA. 265 



developed bifurcate anchor. The simple tooth- or paddle-shaped transverse arms of the 

 latter exhibit a much thickened base rising from the club-shaped swollen terminal portion, 

 and in the larger forms are connected by a distinct lateral fringe on either side. AVhile 

 the upper half of the long anchor spicules, which is for the most part buried in the sponge 

 body, is perfectly smooth, gradually increasing in thickness downwards, the lower half, 

 which becomes gradually narrower, bears small barbs increasing in height and breadth. 

 These are spirally disposed round the shaft, and decrease again in size towards the very 

 end, disappearing entirely a little above the anchor. Thus the much narrowed, and just 

 above the anchor yet slimmer, terminal portion appears quite smooth (PI. LI. fig. 14). 



Among the many Hexactinellids which were trawled by the Challenger near the 

 Little Ki Islands (Station 192, lat. 5° 49' 15" S., long. 132° 14' 15" E.), from a depth of 

 192 fathoms and a blue mud ground, there was a beautiful specimen of a Semperella, 

 which agrees in so many points with Semperella schnltzei, Semper, that I regard it as 

 a young form of the latter. There are indeed some differences, but these may be 

 explained as characteristic of the young form. The specimen has a total length of 

 10"5 cm., of which only 5"6 go to the stretched cylindrical body, and 4*9 cm. to the 

 inferiorly much broadened root process, which is almost wholly enveloped in a Palythoa 

 encrustation (PL LII. fig. 2). At its broadest the body measures 12 mm., and the 

 somewhat bevelled longitudinal edges, which measure about 2 mm. in breadth, anastomose 

 abundantly by means of cross processes. They project somewhat more markedly than 

 in the adult specimen, and are bounded by a fringe of perpendicularly inserted, straight, 

 rod-like spicules (PI. LII. fig. 3), which may be called marginalia, and are almost wholly 

 absent in the large specimen. These slim spicules, which in many places form a con- 

 tinuous garniture and in others are not discoverable, are quite smooth on their internal 

 pointed half, while the free external portion is for the most part beset with small lateral 

 teeth (turned upwards and outwards), and ends in a delicate point, below which there 

 is usually a small club-shaped swelling with two or four lateral teeth. Similar needles 

 also project in the above described young specimens of Poliopogon amadou, both on the 

 oscular margin and on the lateral surface, but are not discoverable on the side of the adult 

 form. This fact seems to make it especially probable that we have here to do with a 

 young specimen, and not with another species, and that the more, since all the other 

 spicules closely resemble in form and disposition those of the larger specimen, as is equally 

 true of the structure of the soft tissue. 



Suborder II. DICTYONINA, Zittel (Pis. LXXI.-CL, CIIL, CIV.). 



Hexactinellida in which the principal hexacts are already at an early stage united 

 into a connected and compact (dictyoual) framework in a more or less regular fashion. 



(zOOIi. CHALL. EXP. — PART LIII. — 1887.) Gfgg 34 



,_j 



