From the taxonomic name Ophiothricidae, a misspelling of Ophiotrichidae, from the generic name Ophiothrix (from Ancient Greek ὄφις (óphis, “snake”) + Ancient Greek θρῐ́ξ (thrĭ́x, “hair”)) + translingual -idae
According to the International Code of Zoological Nomenclature, taxonomic family names are formed from the stem of the name of the type genus (Ophiothrix), which is the genitive singular form after the ending is removed.
The consonants in Ancient Greek θρῐ́ξ (thrĭ́x, “hair”) are due to the underlying χ (aspirated) in the stem becoming ξ (unaspirated) before the nominative singular ending, ς.
The genitive singular form is τρῐχός (trĭkhós) instead of *θρῐχός (*thrĭkhós), due to Grassman's Law, which deaspirates θ to τ when there is an aspirated consonant in the next syllable (the χ). The stem of Ophiothrix is thus "Ophiotrich-"
ophiothricid (plural ophiothricids)