Mantle cylindrical, muscular, 31 cm in length. Very much close to I. illecebrosus, but differs from it in the following points:(1) The largest mantle width
located in the anterior margin (except for gravid female), (2) fin angle
larger than 50°, (3) suckers of the Arms U and V in males usually enlarged,
(4) modified portion of hectocotylus extends more than 25% and hectocotylus
longer than the opposite arm, and (5) fleshy flaps fringed.
Distribution:
Eastern Atlantic and east coast of U.S.A., south of 37°N, Gulf of Mexico, Suriname and Guiana.
Remarks:
In Caribbean Sea, the third species of this genus, I. oxygonius, is known, but no specimens was found in the present collection.