122 ] 
RECORDS OF W.A. MUSEUM. 
nine are 4 (3 + 4) and one is 2 ; of the twenty IIIBr. series seven- 
teen are 2 and three are 4 (3 + 4); the five IVBr. series are all 
4 (3+4) 1 of them are developed on the outermost side of the 
ray, the fifth being by the side of one of these ; the centrodorsal is 
large, thick discoidal, the dorsal pole slightly concave, 5 mm. in 
diameter ; the cirri are 30 mm. to 35 mm. in length, and are 
composed of 44-47 segments ; Pd is rather slender, about 15 mm. 
long, composed of from twenty-seven to twenty-nine segments ; 
(2) forty arms about 100 mm. long; of the ten II Br. series seven 
are 4 {3 + 4) and three are 2 ; sixteen of the IIIBr. series are 
4 (3-I-4) and two are 2 ; two are missing ; the cirri are 30 mm. to 
33 mm. long, and are composed of 37-42 segments ; Pd is 18 mm 
long, rather slender, composed of thirty-seven segments ; (3) forty 
arms about 100 mm. long; the ten IIBr. series are 4 (3-I-4) ; 
twelve of the IIIBr. series are 2 and six are 4 (3-^4); the two 
IVBr. series are 4 (3 + 4) ; the cirri are about 30 mm. long and are 
composed of 38-39 segments; the elongate proximal pinnules are 
slender ; (4) two of the post-radial series are missing ; the three 
post-radial series present consist of eight arms each, two IIBr. and 
four IIIBr. series being present in every case; all of the IIBr. 
series are 4 (3-f4) ; nine of the IIIBr. series are 2 and three 
are 4 (3-44) ; (5) thirty-eight arms, with one IIBr. series missing ; 
the ten IIBr. series are 4(3 + 4); ten of IIIBr. series are 2, six 
being 4 (3+4); (6) thirty-six arms about 100 mm. long ; the ten 
IIBr. series are 4 (3-1-4) : nine of the IIIBr. series are 2 and seven 
are 4 (3 + 4) ; nine of the IIIBr. series are 2 and seven are 4 
(3 + 4) the cirri are 25 mm. to 35 mm. long, composed of 
34-42 segments ; (7) thirty-six arms about 100 mm. long ; five of 
the IIBr. series are 2 and five are 4 (3-f4) I eight of the III Br. 
series are 2 and eight are 4 (3 + 4) ; the cirri are 25 mm. to 30 mm. 
long, composed of 36-40 segments; (8) thirty-four arms about 
100 mm. long; the ten IIBr. series are 4 (3+4); the fourteen 
IIIBr. series are 2 ; the cirri are 25 mm. to 30 mm. long, composed 
of 36-43 segments. The colour in fife is recorded as very variable. 
Remarks. Unfortunately both Zygornetra elegans and- Z. 
microdiscus vary very considerably in their arm structure, and 
examples of both may easily be found which possess more or less 
completely developed the arm structure of the other. For instance, 
the second specimen listed above has seven of the ten IIBr. series 
