ニセツノヒラムシ（）は、ヒラムシの属の一つである。

 特徴 
カラフルで色とりどりなものが多く、毒を意味する警告色となっている。楕円形で、サンゴ礁などに潜んでいることが多い。

アカククリは、このヒラムシに似せているとのこと。

 分類 

WoRMSによる。
 Pseudoceros affinis (Collingwood, 1876)
 Pseudoceros agattiensis Dixit, 2019
 Pseudoceros albicornus (Stimpson, 1857)
 Pseudoceros albomarginatus Hyman, 1959
 Pseudoceros asamusiensis Kato, 1939
 Pseudoceros astrorum Bulnes & Torres, 2014
 Pseudoceros ater Hyman, 1959
 Pseudoceros atraviridis (Collingwood, 1876)
 Pseudoceros atropurpureus Kato, 1934
 Pseudoceros auranticrinis Dixit, Raghunathan & Chandra, 2017
 Pseudoceros bicolor Verrill, 1902
 Pseudoceros bicuti Ramos-Sanchez, Bahia & Rolando Bastida-Zavala, 2020
 Pseudoceros bifasciatus Prudhoe, 1989
 Pseudoceros bimarginatus Meixner, 1907
 Pseudoceros bipurpureus Dixit, 2021
 Pseudoceros bolool Newman & Cannon, 1994
 Pseudoceros buskii (Collingwood, 1876)
 Pseudoceros caeruleocinctus Hyman, 1959
 Pseudoceros caeruleopunctatus Palombi, 1928
 Pseudoceros canadensis Hyman, 1953
 Pseudoceros cardinalis Haswell, 1907
 Pseudoceros cardiosorus (Schmarda, 1859)
 Pseudoceros cerebralis (Kelaart, 1858)
 Pseudoceros chloreus Marcus, 1949
 Pseudoceros clavicornis (Schmarda, 1859)
 Pseudoceros coccineus (Stimpson, 1857)
 Pseudoceros colemani Prudhoe, 1977
 Pseudoceros collingwoodi Laidlaw, 1903
 Pseudoceros concinnus (Collingwood, 1876)
 Pseudoceros confusus Newman & Cannon, 1995
 Pseudoceros contrarius Newman & Cannon, 1995
 Pseudoceros corallophilus Hyman, 1954
 Pseudoceros cruentus Newman & Cannon, 1998
 Pseudoceros devisii Woodworth, 1898
 Pseudoceros dimidiatus von Graff, 1893 プセウドセロス・ディミディアートゥス
 Pseudoceros dulcis Kelaart, 1858
 Pseudoceros duplicinctus Prudhoe, 1989
 Pseudoceros exoptatus Kato, 1938
 Pseudoceros felis Newman & Cannon, 1994
 Pseudoceros ferrugineus (Hyman, 1959)
 Pseudoceros flavomaculatus Graff, 1893
 Pseudoceros flavomarginatus Laidlaw, 1902
 Pseudoceros fulminatus (Stimpson, 1855)
 Pseudoceros fuscogriseus Hyman, 1959
 Pseudoceros fuscopunctatus Prudhoe, 1977
 Pseudoceros fuscus (Kelaart, 1858)
 Pseudoceros galatheensis Dixit, Raghunathan & Chandra, 2017
 Pseudoceros galaxea Dixit, 2021
 Pseudoceros gamblei Laidlaw, 1902
 Pseudoceros glaucus Prudhoe, 1989
 Pseudoceros goslineri Newman & Cannon, 1994
 Pseudoceros gravieri Meixner, 1907
 Pseudoceros griseus Hyman, 1959
 Pseudoceros guttatomarginatus (Stimpson, 1855)カツウラニセツノヒラムシ
 Pseudoceros habroptilus Hyman, 1959
 Pseudoceros haddoni (Laidlaw, 1903)
 Pseudoceros harrisi Bolanos, Quiroga, & Litvaitis, 2007
 Pseudoceros heronensis Newman & Cannon, 1994
 Pseudoceros imitatus Newman & Cannon, 1994
 Pseudoceros imperatus Newman & Cannon, 1998
 Pseudoceros indicus Newman & Schupp, 2002
 Pseudoceros intermittus Newman & Cannon, 1995
 Pseudoceros interruptus (Stimpson, 1855)
 Pseudoceros irretitus Newman & Cannon, 1998
 Pseudoceros japonicus (Stimpson, 1857)
 Pseudoceros jebborum Newman & Cannon, 1994
 Pseudoceros josei Newman & Cannon, 1998
 Pseudoceros juani Bahia et al., 2014
 Pseudoceros kelaarti (Collingwood, 1876)
 Pseudoceros kentii Graff, 1893
 Pseudoceros kylie Newman & Cannon, 1998
 Pseudoceros lacteus (Collingwood, 1876)
 Pseudoceros lactolimbus Newman & Cannon, 1998
 Pseudoceros laingensis Newman & Cannon, 1998
 Pseudoceros langamaakensis Faubel, 1983
 Pseudoceros laticlavus Newman & Cannon, 1994
 Pseudoceros latissimus type A (Schmarda, 1859)
 Pseudoceros leptostictus Bock, 1913
 Pseudoceros limbatus Leuckart, 1828
 Pseudoceros lindae Newman & Cannon, 1994
 Pseudoceros liparus Marcus, 1950
 Pseudoceros litoralis Bock, 1913
 Pseudoceros lividus Prudhoe, 1982
 Pseudoceros luteus (Plehn, 1898)
 Pseudoceros macroceraeus Schmarda, 1859
 Pseudoceros maculatus (Pease, 1860)
 Pseudoceros maximum Lang, 1884
 Pseudoceros maximus-type A Lang, 1884
 Pseudoceros meenae Dixit, Sivaperuman & Raghunathan, 2018
 Pseudoceros memoralis Kato, 1938
 Pseudoceros mexicanus Hyman, 1953
 Pseudoceros microcelis Prudhoe, 1989
 Pseudoceros microceraeus (Schmarda, 1859)
 Pseudoceros micropapillosus Kato, 1934
 Pseudoceros monostichos Newman & Cannon, 1994
 Pseudoceros montereyensis Hyman, 1953
 Pseudoceros mororum Cuadrado, Moro & Norena, 2017
 Pseudoceros mossambicus Prudhoe, 1989
 Pseudoceros mulleri (Delle Chiaje, 1829)
 Pseudoceros niger (Stimpson, 1857)
 Pseudoceros nigrocinctus (Schmarda, 1859)
 Pseudoceros nigropunctatus Dixit, Raghunathan & Chandra, 2017
 Pseudoceros nipponicus Kato, 1944
 Pseudoceros ouini Newman & Cannon, 1994
 Pseudoceros ovimaculatus Prudhoe, 1989
 Pseudoceros paradoxus Bock, 1927
 Pseudoceros paralaticlavus Newman & Cannon, 1994
 Pseudoceros periaurantius Newman & Cannon, 1994
 Pseudoceros periphaeus Bock, 1913
 Pseudoceros peripurpureus Newman & Cannon, 1994
 Pseudoceros perviolaceus (Schmarda, 1859)
 Pseudoceros pius Kato, 1938
 Pseudoceros pleurostictus Bock, 1913
 Pseudoceros punctatus Laidlaw, 1902
 Pseudoceros purpureus (Kelaart, 1858)
 Pseudoceros rawlinsonae Bolanos, Quiroga, & Litvaitis, 2007
 Pseudoceros regalus Laidlaw, 1903
 Pseudoceros reticulatus Yeri & Kaburaki, 1918
 Pseudoceros rubellus Laidlaw, 1903
 Pseudoceros rubronanus Newman & Cannon, 1998
 Pseudoceros rubrotentaculatus Kaburaki, 1923
 Pseudoceros sagamianus Kato, 1937
 Pseudoceros sapphirinus Newman & Cannon, 1994 プセウドセロス・サップフィリヌス
 Pseudoceros scintillatus Newman & Cannon, 1994
 Pseudoceros scriptus Newman & Cannon, 1998
 Pseudoceros stellans Dixit, 2019
 Pseudoceros stimpsoni Newman & Cannon, 1998
 Pseudoceros striatus Kelaart, 1858
 Pseudoceros susanae Newman & Anderson, 1997
 Pseudoceros texanus Hyman, 1955
 Pseudoceros tigrinus Laidlaw, 1902
 Pseudoceros tomiokaensis Kato, 1938
 Pseudoceros tristriatus Hyman, 1959
 Pseudoceros variegatus Prudhoe, 1989
 Pseudoceros velutinus (Blanchard, 1847)
 Pseudoceros verecundus Newman & Cannon, 1994
 Pseudoceros vinosus Meixner, 1907
 Pseudoceros vishnui Dixit, Raghunathan & Chandra, 2017
 Pseudoceros yessoensis Kato, 1937
 Pseudoceros zebra (Leuckart, 1828)
 Pseudoceros zeylanicus (Kelaart, 1858)