278 Mr. R. Kirkjjatrick on the MonaxonelUda 



The fine specimen (no. 184) which constitutes the type of 

 the new species is 24 cm. wide and 25"6 cm. high. 

 Locality. "Winter Quarters, 28-130 fath. 



My. villa decepta, sp. n. 



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 verti- 

 cally dressed acanthostyles, each surrounded by tufts of 

 ectosomal spicules. Tiie other, which incrusts the branch of 

 a Polyzoon, 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 tliin incrustation at first sight 

 resembles iXxat oi 2i 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. 



Tlie ectosomal spicules are partly arranged in paniculate 

 tufts, partly lying tangentially in the dermal membrane. 



Sincules. — Megascleres : choanosomal acanthostyles, 468 X 

 23*5 /i, curved, spined at the head only, with aubtornote 

 points. Ectosomal strongyles, 238 x 4-6 /x, straight, smooth, 

 cylindrical, usually with a pointed mucro at one end. 



Microscleres : arcuate isocheke, 19*5 /u, long, 5*6 /* broad, 

 palmate tooth 8 /a long, ovoid, with rounded distal edge ; with 

 thick curved shaft ; with tongue-shaped al^ about 8 p, long. 



Isancorse unguiferse, 15'3 /x long, with slender, curved, 

 sometimes wavy shaft, with three sharp claw-like teeth at 

 each end. 



Chelate bipocilla 8 ^i long, with deeply curved shaft with 

 spathulate ends each with three triangular denticles ; these 

 spicules are fairly common and not accidental. 



There are also several isochelse arcuata3 in which the alae 

 and denticle are replaced at one end by a spoon-like lamella. 



The presence in Myxilla of chelate bipocilla similar in 

 many respects to those found in the new species lophon spatu- 

 latus and I. Jlahello-digitatus is exceptional. In other respects 

 the spiculation is that of a typical Myxilla. The isochelae 

 arcuatae, though only half the length, resemble in shape 

 those of Myxilla nohilis, R. & D., from off the Rio de la 

 Plata, and M. digitata, R. & D., from the Cape of Good 

 Hope. The new species, again, closely resembles Myxilla 

 iophonoides^ Swartszewsky (Mem. Soc. Nat. Kieff, xx. p. 340^ 



