of the National Antarctic Expedition. 285 



hispid under a lens. With several small scattered oscules, 

 about 1 mm. in diameter, level with the surface. Flagellated 

 chambers aphodal, oval, 31 X 21 /tt. 



Skeleton formed of long longitudinal lines of spicule-fibres 

 about 100 /i thick, not forming a definite central axis, 

 radiating out in plumose manner to the surface ; with a few 

 isolated spicules arranged in a scalariform manner at right 

 angles to main fibres. Spongin not perceptible. 



ISpicules. — Megascleres : oxeas, 452 x 19*5 yu., curved at 

 centre, attenuating gradually to sharp points slightly planed 

 away on inner aspect. Microscleres : canonochelai, somewhat 

 shuttle-shaped, 45"5 /* long by 22'75/i broad, with the two 

 teeth fused to form a bridge, and with a semicircuhir lamella 

 passing upwards from the shaft and downwards from the 

 dental bridge, both lamellae being nearly on the same plane 

 and nearly meeting, the lamellae sometimes with basal 

 tubercles. Developmental forms in shape of thin, oval, 

 linear bodies^ the oval at first not being complete. 



Tlie unique specimen representing the new genus and 

 species is 12"5 cm. long and 1 cm, in breadth at the centre. 

 The body attenuates to fine ends, and apparently has not 

 been attached to anything. 



The remarkable canonochelse recall to mind the sphaeran- 

 coree of MelonancJiora, but the latter spicules have three pairs 

 of fused teetli. 



I'he canonoclielffi are scattered about in the choanosome in 

 considerable numl)ers. Tlie shape may be compared with 

 an oval basin with the bottom cut out, and with two semi- 

 circular lids or lamellai |^xissing horiz^jntally from the upper 

 edge of the basin, so as to nearly meet ; further, it is 

 necessary to imagine such a basin turned up on its side. 



The earliest developmental forms have an elongated 

 C-shape ; then the open C becomes a closed oval ; by this 

 time the falx at each end is perceptible, and the beginnings 

 of the lamellae appear. A further change leads to a marked 

 asymmetry, the thin oval ring becoming a broad band by 

 widening in a direciion away from the edges whence the 

 lamellai arise. 



LocaUly. Winter Quarters, 130 fath. 



HOPLAKITHAKA *, gen. IIOV. 



Mycalina3 possessing exotyles with large spherical spined 

 heads and with fimbriated placocheles. 



* <J'n\a (])1. of ottXos), iiriuour ; Kiddpa, a guitar. 



