A review of pygal-furrowed Synallactidae (Echinodermata: Holothuroidea), with new species from the Antarctic, Atlantic and Pacific oceans Author O'Loughlin, P. Mark Author Ahearn, Cynthia text Memoirs of Museum Victoria 2005 2005-12-31 62 2 147 179 https://museumsvictoria.com.au/collections-research/journals/memoirs-of-museum-victoria/volume-62-issue-2-2005/pages-147-179/ journal article 10.24199/j.mmv.2005.62.5 1447-2554 12208025 Molpadiodemas helios sp. nov. Figures 1a , 3l , 4q–t , 6c, d Material examined . Holotype . Central Pacific Ocean , Clipperton Fracture Zone , 13°13'N , 129°53'W , 4877 m , RV Governor Ray , Ocean Minerals Co. , 15 Feb 1980 , USNM E31106 . Paratypes . Type locality, 13°13'N , 129°52-53'W, 4724–4892 m , 1980, USNM E31104 (1) , E31117 (1), E31134 (1), E31137 (1), E31141 (1), NMV F101852 (1) , F101854 (1). Other material . Type locality, 13°13'N , 129°52–55'W, 4755–4938 m , 1980, USNM E31097 (1) , E31103 (1), E31105 (1), E31110– E31114 (5), E31118 (1), E31129 (2), E31133 (1), E31138– E31140 (3), E31144 (1), E48515 (1), NMV F101853 (1). Description . Up to 170 mm long; body wall soft-leathery to semi-gelatinous; no body attachments (encrustations); body rounded in transverse section, lacking brim; tentacles with about 10 large conical pointed digits peripherally, some digits bifid; tube feet soft, white to semi-translucent, scattered and lying all over body, most dense around oral and pygal areas, up to 2.0 mm long, 0.15 mm diameter, frequently cylindrical digitate erect orally and pygally, typically 0.8 mm long, 0.2 mm diameter; ossicles in tentacles and gonad; tentacle ossicles sparse to rare, thick to thin rods up to 150 µm long, rare branches, rare perforations at ends or branches joined to form perforations, lacking spines, sometimes swollen mid-rod; gonad tubules with abundant irregular thin rods, some irregularly branched, branches sometimes joined to create perforations, lacking spines, swellings rare, up to 280 Μm long. Colour . Body off-white to grey, frequently semi-translucent, smaller specimens sometimes with pale brown. Etymology . From the Greek helios (sun), referring to the sunflower appearance of the radiating tentacle digits. Distribution . Central Pacific Ocean, Clipperton Fracture Zone, 13°13'N , 129°53'W , 4724–4938 m . Remarks . Amongst Molpadiodemas species , the distinguishing characters of M. helios are: relatively prominent soft tube feet scattered over the body, sometimes cylindrical and erect posteriorly and anteriorly; prominent conical tentacle digits; predominantly smooth rod ossicles in gonad.