EEPORT ON THE MONAXONIDA. 89 



numerous, long, slender, hair-like processes, broadest at the base, where they join the 

 stem. They are arranged very regularly in four rows, so as to lie in two vertical 

 planes which intersect each other at right angles. The interval between each two 

 successive processes in a row is about 1-5 mm.; the processes themselves may attain the 

 great length of 17 mm. Colour in spirit pale yellowish. 



Sheleton. — A stout axis of spiculo-fibre runs through the stem, branching to form 

 the roots and giving off above the hair -like processes (pinnag). 



Spicules. — (a) Megasclera ; smooth, slender styli, broadest in the middle and 

 tapering rather abruptly to a fairly sharp point at the apex. They may reach the great 

 length of over 2 mm., and have a diameter of about 0'019 mm. Their length, however, 

 varies much, and is generally less than that given. They are very firmly bound together 

 in fibres, and it is difficult to get one separate for purposes of measurement, (h) Micro- 

 sclera ; of two kinds ; (1) anisochelae, with long, curved shaft and very unequal, claw-like 

 extremities ; they are very small, measuring about 0"025 mm. in length, and closely 

 resemble those figured by Sars^; (2) rather large, smooth, simple sigmata, measuring 

 about 0-13 by 0'007 mm. 



The anatomy of the soft parts of this remarkable species has always been a mystery 

 and must still remain so, for unfortunately the only specimen obtained by the Challenger 

 was found dried up when we came to describe it. It will be seen that, as regards 

 external form, the Challenger variety diifers very considerably from those described 

 and figured by Sars.^ It also differs widely in appearance from the " Porcupine " 

 specimens, now in the British Museum. It resembles in slenderness and delicacy 

 Cladorhiza pennatula, Schmidt,^ which has, however, the lateral pinnte developed 

 only in one plane. Two remarkable features about this sponge are the very great depth 

 at which it occurs and the locality ; Sars* says : — " I have only found this remarkable 

 sponge in one single locality, namely at the fishing station Skraaven in Lofoten at the 

 great depth of 300 fathoms on soft clay bottom"; whereas the Challenger variety comes 

 from a depth of 2750 fathoms, in the middle of the Pacific Ocean. The "Porcupine" 

 specimens were obtained between Scotland and the Fseroe Islands, Schmidt's in the 

 Skagerrack, and Hansen's (those of which the localities were preserved) either between 

 Norway and the Fgeroe Islands, or near the west coast of Spitzbergen, one of these 

 stations having a depth of 1215 fathoms; but uncertainty overhangs the identifi- 

 cations of the species by both these authors {e.g., Hansen perhaps includes Carter's 

 so-called variety corticocancellata,, which may probably be regarded as a distinct 

 species). 



Locality.— Station 274, September 11, 1875; lat. 7° 25' S., long. 152° 15' W.; 



1 Remarkable Forms of Animal Life, pt. i. pi. vi. figs. 31, 32, a. 



2 Loc. cit, figs. 16, 17. 



3 Jahresb. Comm. Wiss. Untersuch. d. deutsch. Mecre, Jahrg. i., ii., p. 119, pi. i. figs. 14-16. 

 * Loc. cit., p. 68. 



(zooL. CHALL. EXP. — PART Lix. — 1887.) N'nn 12 



