The Echinoid Directory

• Test flat with sharp and thin margins; usually slightly wider than long.
• Apical disc monobasal with four gonopores.
• Test with four ambulacral lunules and an anal lunule in the type.
• Paired interambulacra disjunct on oral surface, but posterior interambulacrum continuous.
• Basicoronal circlet pentastellate with interambulacral plates strongly projecting.
• Periproct opening on inner margin of first pair of post-basicoronal plates and at inner edge of anal lunule.
• Internal butressing well developed; composed of dense mesh. Pillers separate the buccal cavity from the intestinal space.
• Food grooves bifurcating at edge of basicoronals and highly branched distally. Wide space between ambulacral lunule margin and food groove.

Early Pliocene to Recent, America.

Echinodiscus quinquesperforata Leske, 1778, p. 197 (= Mellita testudinata Klein, 1853), by subsequent designation of Pomel, 1883, p. 197.

• M. quinquesperforata (Leske, 1778); Pleistocene to Recent, Caribbean and western Atlantic shelf from the Mississippi delta to southern Brazil.
• M. tenuis Clark, 1940; Recent, eastern Gulf of Mexico from southen Florida to western Louisiana.
• M. isometrica Harold & Telford 1990; Recent, east coast of USA.
• M. notabilis Clark, 1947; Recent, central west coast of Mexico and Central America.
• M. kanakoffi Durham, 1961; Pleistocene to Recent California to Panama.

Clypeasteroida; Scutellina; Scutelliformes; Scutellidea; Mellitidae.
 

Harold & Telford (1990) give an excellent review of this genus together with a key to the species. It differs from Leodia in having no lunule in the anterior ambulacrum (see Mooi & Peterson 2000 for discussion). Differs from Lathonia by its bidentate pedicellariae enlarged terminal teeth and wide space between food grooves and ambulacral lunule edges

According to Mooi & Peterson (2000) Miocene records of Mellita in the literature are based on out-dated age assignments and misidentifications.

Coppard, S. E. 2016. A new genus of mellitid sand dollar (Echinoidea: Mellitidae) from the eastern Pacific coast of the Americas. Zootaxa, 4111, 158-166.

J. W. Durham, 1961. The echinoid Mellita in the Pacific coast Cenozoic. Los Angeles County Museum Contributions in Science 48, 3-12.

Harold, A. S. & Telford, M. 1990. Systematics, phylogeny and biogeography of the genus Mellita (Echinoidea: Clypeasteroida). Journal of Natural History 24, 987-1026.

R. Mooi & D. Peterson 2000. A new species of Leodia (Clypeasteroida: Echinoida) from the Neogene of Venezuela and its importance in the phylogeny of mellitid sand dollars. Journal of Paleontology 74, 1083-1092.