TETRAXONIDA. 27 



Echinating acanthostyles, :219 x 18'75/t (without including spines), larger spines 

 situated on the head 9 fj. long. 



Ectosomal amphityles, 35f> x-11 n straight, very slightly fusiform, subtylote, and 

 with a small mucro at each end. 



Microscleres, none. 



Myxilla victoriana Dendy (Plalichondria pustulosa 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 fins. A third 

 specimen (No. 38) on Ilornera was obtained from east end of Barrier, 100 fins., 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 derejitii Kirkpatrick (10a. p. -'I*.) 



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 owin- 

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

 ectosomal spicules. The other, which incrusts the branch of a Poly/oon, is thicker, and 

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

 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 

 Hymerrhaphia ; 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 iii paniculate tufts, partly lying 

 tangentially in the dermal membrane. 



Spicules. Mcgasderes. ( 'hoanosomal acauthostyles, 4G8 X 23* 5 /it, curved, 

 spincd at the head only, with sub-tornote points. Ectosomal strougyles 238 X 4'G/i, 

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



Microscleres. Arcuate isocliehu, 19 - 5/i long, 5'6/x broad, palmate tooth 8 /* long 

 ovoid, with rounded distal edge; with thick curved shaft : with tongue-shaped ala; 

 about 8 fj. long. 



Isaucorae uuguiferae, 15'3ju 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 spatlmlatc ends each 

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



