Cardiidae
Baineann an t-alt seo le fine mhór moileasc ina bhfuil thart ar 200 speiceas; má tá suim agat sa speiceas is coitianta ar chóstaí na hÉireann (Cerastoderma edule), féach Ruacan coiteann.

Is moileasc mara débhlaoscach inite é ruacan. Cé go dtugtar “ruacan” ar go leor débhlaoscach inite, is iad na speicis san fhine tacsanomaíochta Cardiidae na fíor-ruacain.

Cónaíonn ruacain ar thránna gainimh ar foscadh timpeall an domhain. Bíonn an sliogán cruinn agus siméadrach go déthaobhach, ar dhéanamh croí nuair a bhreathnaítear air ón deireadh. Feictear easnacha gathacha, spásáilte go cothrom, ar an sliogán sa chuid is mó de na géinis; is eisceacht é Laevicardium, na ruacain uibhe, a bhfuil sliogáin an-mhín orthu.

Tá an ruacan in ann a shliogán a dhúnadh go hiomlán; is é sin le rá, níl aon “bhearna” idir an dá thaobh. Cé go bhfuil cosúlacht idir sliogán an ruacain agus an muirín mar gheall ar na heasnacha, is féidir iad a idirdhealú ó thaobh moirfeolaíochta de, sa mhéid is nach bhfuil “cluaisíní” (cnapa beaga ar cruth cluaise i ngar don inse) ag an ruacan.

Tugtar an t-ainm “ruacan” ar roinnt speiceas nach bhfuil san fhine Cardiidae; mar shampla, an ruacan con (Glycymeris glycymeris), an ruacan croí (Glossus humanus), an ruacan cruinneánach (Sphaerium corneum), agus an ruacan piseánach (Pisidium casertanum). Ar an lámh eile, ní thugtar “ruacan” ar gach speiceas de chuid Cardiidae; mar shampla, is ball den fhine é an breallach mór.

Tá níos mó ná 205 speiceas beo san fhine, agus go leor foirmeacha iontaise eile.

Faightear an ruacan coiteann (Cerastoderma edule) go forleathan timpeall chóstaí Thuaisceart na hEorpa, chomh fada siar le hÉirinn, chomh fada ó thuaidh le Muir Barents, chomh fada soir leis an Iorua, agus chomh fada ó dheas leis an tSeineagáil.

Géinis

 Acanthocardia Gray, 1851
 † Acobaecardium Paramonova, 1986 
 Acrosterigma Dall, 1900
 Adacna Eichwald, 1838
 Afrocardium Tomlin, 1931
 † Agnocardia Stewart, 1930 
 † Aktschagylocardium Danukalova, 1996 
 Americardia Stewart, 1930
 † Andrusovicardium Paramonova, 1986
 † Anechinocardium Hickman, 2015 
 Apiocardia Olsson, 1961
 † Apscheronia Andrusov, 1903 
 † Arcicardium P. Fischer, 1887 
 † Arpadicardium Eberzin, 1947 
 † Austrocardium Freneix & Grant-Mackie, 1978
 † Avicardium V. P. Kolesnikov, 1950 
 † Avicularium Gray, 1853 
 † Aviculocardium Bagdasarian, 1978
 † Bosphoricardium Eberzin, 1947 
 Bucardium Gray, 1853
 † Budmania Brusina, 1897
 † Byssocardium Tournouër, 1882 
 † Caladacna Andrusov, 1917 
 Cardium Linnaeus, 1758
 † Caspicardium Astaf'yeva, 1955 
 Cerastoderma Poli, 1795
 † Chartoconcha Andrusov, 1907 
 † Chokrakia S. V. Popov, 2001 
 Ciliatocardium Kafanov, 1974
 Clinocardium Keen, 1936
 Corculum Röding, 1798
 Ctenocardia H. Adams & A. Adams, 1857
 † Dacicardium Papaianopol, 1975 
 Dallocardia Stewart, 1930
 Didacna Eichwald, 1838
 † Didacnoides Astaf'yeva, 1960 
 † Didacnomya Andrusov, 1923 (neamhchinnte)
 † Digressodacna Davitashvili & Kitovani, 1964 
 Dinocardium Dall, 1900
 Discors Deshayes, 1858
 † Diversicostata Vassoevich & Eberzin, 1930 
 † Ecericardium Eberzin, 1947 
 † Eoprosodacna Davitashvili, 1934 
 † Ethmocardium White, 1880
 Europicardium Popov, 1977
 † Euxinicardium Eberzin, 1947 
 Fragum Röding, 1798
 Freneixicardia J. A. Schneider, 2002
 Frigidocardium Habe, 1951
 Fulvia Gray, 1853
 † Gilletella Marinescu, 1973 
 Glans Megerle von Mühlfeld, 1811
 Goethemia Lambiotte, 1979
 † Goniocardium Vasseur, 1880 
 † Granocardium Gabb, 1869 
 † Habecardium Glibert & van de Poel, 1970
 † Hedecardium Marwick, 1944
 † Hellenicardium S. V. Popov & Nevesskaja, 2000
 Hippopus Lamarck, 1799
 † Horiodacna Stefanescu, 1896 
 Hypanis Pander in Menetries, 1832
 † Integricardium Rollier, 1912 
 Keenaea Habe, 1951
 Keenocardium Kafanov, 1974
 † Korobkoviella Merklin, 1974 
 † Kubanocardium Muskhelishvili, 1965 
 Laevicardium Swainson, 1840
 † Lahillia Cossmann, 1899 
 † Limnodacna Eberzin, 1936 
 † Limnopagetia Schlickum, 1963
 † Limnopappia Schlickum, 1962 
 Lophocardiium P. Fischer, 1887
 † Loxocardium Cossmann, 1886 
 Lunulicardia Gray, 1853
 † Luxuridacna Papaianopol, 1980 
 † Lymnocardium Stoliczka, 1870 
 Lyrocardium Meek, 1876
 Maoricardium Marwick, 1944
 † Merklinicardium S. V. Popov, 1982  (neamhchinnte)
 † Metadacna Eberzin, 1959 
 Microcardium Keen, 1937
 Microfragum Habe, 1951
 † Miricardium Paramonova, 1986 
 Monodacna Eichwald, 1838
 † Moquicardium Eberzin, 1947 
 † Myocardia Vest, 1861  (neamhchinnte)
 † Nargicardium Eberzin, 1947
 Nemocardium Meek, 1876
 † Obsoletiformes Kojumdgieva, 1969
 † Omanidacna Harzhauser & Mandic, 2008 
 † Oraphocardium Eberzin, 1949 
 † Orthocardium Tremlett, 1950 
 † Oxydacna Davitashvili, 1930 
 † Pachydacna Eberzin, 1955 
 † Pannonicardium Stevanović, 1951 
 † Panticapaea Andrusov, 1923 
 Papillicardium Sacco, 1899
 Papyridea Swainson, 1840
 † Papyrocardium Gabuniya, 1953  (neamhchinnte)
 † Paradacna Andrusov, 1909 
 † Parapscheronia Eberzin, 1955 
 Parvicardium Monterosato, 1884
 † Parvidacna Stevanović, 1950 
 † Phyllocardium P. Fischer, 1887 
 † Plagiocardium Cossmann, 1886 
 † Plagiodacna Andrusov, 1903 
 † Plagiodacnopsis Andrusov, 1923 
 † Planacardium Paramonova, 1971 
 † Plicatiformes Kojumdgieva, 1969 
 † Pontalmyra Stefanescu, 1896 
 Pratulum Iredale, 1924
 † Prionopleura Eberzin, 1949
 Procardium ter Poorten & La Perna, 2017
 † Prophyllicardium Jekelius, 1944  (neamhchinnte)
 † Prosochiasta Eberzin, 1959 
 † Prosodacna Tournouër, 1882 
 † Prosodacnomya Eberzin, 1959 
 † Protocardia Beyrich, 1845 
 † Protoplagiodacna Stevanović, 1978
 † Pseudocatillus Andrusov, 1903 
 Pseudofulvia Vidal & Kirkendale, 2007
 † Pteradacna Andrusov, 1907 
 † Raricardium Paramonova, 1986 
 † Replidacna Jekelius, 1944 
 Ringicardium
 † Schedocardia Stewart, 1930 
 † Schirvanicardium Andreescu, 1974 
 Serripes Gould, 1841
 † Stylodacna Stefanescu, 1896 
 † Submonodacna Livental, 1931 
 † Tauricardium Eberzin, 1947 
 Trachycardium Mörch, 1853
 Tridacna  Bruguière, 1797, na ollbhreallaigh
 † Tschaudia Davitashvili & Kitovani, 1964
 † Turcmena G. I. Popov, 1956 
 Trigoniocardium
 Vasticardium Iredale, 1927
 Vepricardium Iredale, 1929
 † Uniocardium Capellini, 1880
 † Yokoyamaina Hayami, 1958 
 † Zamphiridacna Motaş, 1974

Gallery

Tagairtí 

Moilisc
Débhlaoscaigh