TETRAXONIDA. 27 



Echinating acantliostyles, 219 X 18*75^ (without iucludiug spiues), larger spines 

 situated ou the head 9 fx long. 



Ectosomal ampliityles, 35G x 1 1 /^ straight, very slightly fusiform, sulitylote, and 

 with a small mucro at each end. 



Microscleres, none. 



Myxilla victoriana Dendy {Halichondria piistidosa Carter), (5. p. 30), would come 

 under this genus, although, at the same time, it is in possession of isochelae, and the 

 heads of the styli of the main fibres occasionally have a slight indication of spination 



Two fragments (No. 123) were dredged off Coulman Island in 100 fms. A third 

 specimen (No. 38) on Hornera was obtained from east end of Barrier, 100 fms., bottom 

 mud, stones, and rocks. 



II. SUB-FAMILY MYCALINAE, Thiele. 



I. GROUP Myxilleae, Lundbeck. 



Myxilla decepta. 



(Plate XXII., figs. l-2a, and Plate XXV., fig. 3a-f ) 



1907. Myxilla decepta Kirkpatrick (10a. p. 27>^.) 



Description. There are two very small specimens of this species. One is in the 

 form of an extremely thin incrustation on a piece of rock ; the surface is pilose owing 

 to the projection of vertically dressed acanthostyles, each surrounded by tufts of 

 ectosomal spicules. Tlie other, which incrusts the branch of a Polyzoon, is thicker, and 

 the surface here is partly smooth, partly provided with minute sharp-pointed couules 

 supported by acanthostyles. The colour of both specimens is reddish brown. 



The skeleton in the very thin incrustation, at first sight, resembles that of a 

 Uymerrltaijliia ; each vertical acanthostyle is isolated, and with its head on the base 

 and its pointed end projecting. In the thicker specimen it is possible to make out 

 primary and secondary lines of skeletal fibres. 



The ectosomal spicules are partly arranged in paniculate tufts, partly lying 

 tangentially in the dermal membrane. 



Spicules. Megascleres. Choanosomal acanthostyles, 4G8 x 23"5/x, curved, 

 spined at the head only, with sub-tornote points. Ectosomal strongyles 238 x 4"6/x, 

 straight, smooth, cylindrical, usually with a pointed mucro at one end. 



Microscleres. Arcuate isochelae, 1 9 • 5 /x long, 5 • 6 /x broad, palmate tooth 8 /x long 

 ovoid, witli rounded distal edge ; with thick curved shaft ; with tongue-shaped alee 

 about 8 /I long. 



Isaucorse unguiferae, 15" 3^ long, with slender, curved, sometimes wavy shaft, 

 with three sharp claw-like teeth at each end. 



Chelate bipocilla 8/x long, with deeply curved shaft with spathulate ends each 

 with three triangular denticles ; these spicules are fairly common and not accidental. 



