760 " THETIS " SCIENTIFIC RKSDLTS. 



Ocean, including the north coast of Australia, and thence to the 

 Gilbert Islands and Southern Japan. 



Remarks. — Comatula rotalaria, Lamarck, 1816, must be elimi- 

 nated from the synonymy of this species, an examination of the 

 types at Paris having shown it to be identical with Bell's Actino- 

 7net7-a paucicirra ; the Alecto wahlbergli, J. Miiller^ 1841, 

 from South Africa, formerly considered the same as this species, 

 is in reality very distinct, being inuch more like C. trichoptera ; 

 Acthiometra meyeri and A. anmdata, placed in the synonymy 

 of this species by Carpenter, are in reality the same as his Actino- 

 metra valida. 



Family ZYCOMETRID^, J. H. Clark. 



Genus Z Y G M E T R A, A. H. Clark. 



Zygometra, 1907, A. H. Clark, Smiths. Miscell. Coll. (Quarterly 

 Issue), vol. 50, p. 347 (Antedon microdiscus, Bell, 1884). 



Diferential Characters. — The species of the genus Zygometra 

 have the elements of the I Br series united by what appears to be 

 a perfect syzyg}'^, though in reality it is a curious modification of 

 a synarthry which has taken on all the characters of the syzygy. 

 The II Br series, when pi-esent, are 4 (3 + 4). The Australian 

 species have numerous arms, but the East Indian species have 

 only from ten to thirty arms. The lower pinnules are enlarged 

 and stout, but taper to a more or less flagellate tip. The cirri 

 are long, with numerous segments of which the outer bear long 

 dorsal spines. 



Range. — Northern Australia to the Mergui Archipelago, 

 Singapore, Hong Kong, and the Philippine Islands. 



ZYGOMETRA MICRODISCUS {Bell). 



Antedon microdiscus, 1884, Bell, Rep. Zool. Coll. H.M.S. " Alert," 

 p. 163, pi. XV. (Port Mollb, 12 fms.; Nicol Bay, N.W. Aus- 

 tralia). — 1888, P. H. Carpenter, "Challenger" Keport.s, Zool. 

 vol. 26, p. 97, pi. xxxvii., tigs. 4-6 {Prince of Wales Channel, 

 8 fms.}. — 1898, Doderlein, Denkschr. Ges. Jena, vol. viii., 

 p. 473, pi. xxxvi., tigs. 2, 2a [Thursday Island). 



Zygometra microdiscus, 1909, A. H. Clark, Zool. Anzeiger, vol. 

 34, p. 367 {Mermaid Strait, N.W. Australia). 



Differential Characters. — Zygometra microdisctis may be at 

 once distinguished from all the other species of the genus by 

 the almost or quite exclusive presence of division series of 4 

 (3 + 4), and the occurrence of at least four axillaries beyond that 



