(Latin plural genera), 1550s as a term of logic, "kind or class of things" (biological sense dates from c. 1600), from Latin genus (genitive generis) "race, stock, kind; family, birth, descent, origin" (from suffixed form of PIE root *gene- "give birth, beget," with derivatives referring to procreation and familial and tribal groups).
"cartilaginous fish resembling or related to a shark of the genus selachii," 1835; the genus name from Latinized form of Greek selakhos (plural selakhē) "cartilaginous fish," which is of uncertain origin.
horseshoe crab, king crab, representative genus of the biological family Limulidae, 1837, Modern Latin, from Latin limulus "somewhat askance," diminutive of limus "askance." The genus classification involved the number and position of the eyes.
genus of fungi, Modern Latin, from Greek pilos "felt" (see pileated) + bōlos "a clod, clump."
"Australian duck-mole," 1799, from Modern Latin, from Greek platypous, literally "flat-footed," from platys "broad, flat" (from PIE root *plat- "to spread") + pous "foot," from PIE root *ped- "foot." Originally the genus name, but entomologists had given it earlier to a genus of beetles; it was retained for the species after the genus name was changed in 1800 to Ornithorhyncus. OED has Australian platypussary (1945) "enclosure in which platypuses are kept."
1660s, genus of swordfish, from Greek xiphias "swordfish," from xiphos "a sword" (see xiphoid). Related: Xiphioid.