No. 7. — Notes on some Australian and Indo-Pacific Echino- 

 derms. By Hubert Lyman Clark. 



The Trustees of the Australian Museum having placed in my hands 

 the collection of echinoderms made by the "Thetis" in 1898, it has 

 seemed desirable before studying that collection to work over the Aus- 

 tralian material in the M. C. Z. collections and to describe the new forms. 

 I have to thank Mr. Robert Etheridge, Curator of the Museum, for his 

 courteous approval of this plan. I have found that the ophiurans of 

 the genera Pectinura and Ophiopeza offer some peculiar difficulties and 

 it has been necessary to make a very careful study of those genera and 

 their allies. This has led to a complete revision of all the known species 

 of ophiurans of that group (which may be styled Ophiarachna sensu 

 Muller and Troschel -+• Ophiopeza sensu Peters), and I incorporate my 

 results in this paper. 



ASTEROIDEA. 



ASTROPECTINIDAE. 



Astropecten. 



The M. C. Z. collection contains half a dozen Astropectens from the coast of 

 New South Wales. Two of these are without doubt A. polyacanthus M. and T., 

 but the other four are less easy to determine. One was received in exchange 

 from the United States National Museum and is labelled " Astropecten triseria- 

 tus M. & T., Botany Bay, Australia." The other three are undoubtedly the 

 same species and are so labelled, but were received from the Australian Museum, 

 and were collected off Port Jackson. These specimens agree well with Miiller's 

 and Troschel's description of A. triseriatus, except in the most important point. 

 The large spines on the supramarginal plates are in a single series and there is no 

 trace of the second and third series, characteristic of Muller's and Troschel's 

 species, except that on a very few plates a second small spine is present close 

 beside the principal one. I see no reason to doubt that this is the A. triseriatus 

 of Whitelegge's list (Journ. Roy. Soc. N. S. W., 23, p. 200), but that it is the 

 A. triseriatus of Muller and Troschel seems to me very doubtful. Except for 

 the fact that the ventral and marginal spines are strongly flattened instead of 

 being cylindrical, I should have no hesitation in referring these specimens to 

 Sladen's A. acanthifer from the Banda Sea, but the difference in the spines is so 

 marked I hardly think such identification would be correct. 



