HECTOCOTYLI
Noun
hectocotyli
plural of hectocotylus
Source: Wiktionary
HECTOCOTYLUS
Hec`to*cot"y*lus, n.; pl. Hectocotyli. Etym: [NL., fr. Gr. (Zoöl.)
Definition: One of the arms of the male of most kinds of cephalopods, which
is specially modified in various ways to effect the fertilization of
the eggs. In a special sense, the greatly modified arm of Argonauta
and allied genera, which, after receiving the spermatophores, becomes
detached from the male, and attaches itself to the female for
reproductive purposes.
Source: Webster’s Unabridged Dictionary 1913 Edition